repair_service: debug stop

Seen the following unexplained assertion failure with
pytest -s -v --scylla-version=local_tarball --tablets repair_additional_test.py::TestRepairAdditional::test_repair_option_pr_multi_dc
```
INFO  2024-05-27 11:18:05,081 [shard 0:main] init - Shutting down repair service
INFO  2024-05-27 11:18:05,081 [shard 0:main] task_manager - Stopping module repair
INFO  2024-05-27 11:18:05,081 [shard 0:main] task_manager - Unregistered module repair
INFO  2024-05-27 11:18:05,081 [shard 1:main] task_manager - Stopping module repair
INFO  2024-05-27 11:18:05,081 [shard 1:main] task_manager - Unregistered module repair
scylla: repair/row_level.cc:3230: repair_service::~repair_service(): Assertion `_stopped' failed.
Aborting on shard 0.
Backtrace:
  /home/bhalevy/.ccm/scylla-repository/local_tarball/libreloc/libseastar.so+0x3f040c
  /home/bhalevy/.ccm/scylla-repository/local_tarball/libreloc/libseastar.so+0x41c7a1
  /home/bhalevy/.ccm/scylla-repository/local_tarball/libreloc/libc.so.6+0x3dbaf
  /home/bhalevy/.ccm/scylla-repository/local_tarball/libreloc/libc.so.6+0x8e883
  /home/bhalevy/.ccm/scylla-repository/local_tarball/libreloc/libc.so.6+0x3dafd
  /home/bhalevy/.ccm/scylla-repository/local_tarball/libreloc/libc.so.6+0x2687e
  /home/bhalevy/.ccm/scylla-repository/local_tarball/libreloc/libc.so.6+0x2679a
  /home/bhalevy/.ccm/scylla-repository/local_tarball/libreloc/libc.so.6+0x36186
  0x26f2428
  0x10fb373
  0x10fc8b8
  0x10fc809
  /home/bhalevy/.ccm/scylla-repository/local_tarball/libreloc/libseastar.so+0x456c6d
  /home/bhalevy/.ccm/scylla-repository/local_tarball/libreloc/libseastar.so+0x456bcf
  0x10fc65b
  0x10fc5bc
  0x10808d0
  0x1080800
  /home/bhalevy/.ccm/scylla-repository/local_tarball/libreloc/libseastar.so+0x3ff22f
  /home/bhalevy/.ccm/scylla-repository/local_tarball/libreloc/libseastar.so+0x4003b7
  /home/bhalevy/.ccm/scylla-repository/local_tarball/libreloc/libseastar.so+0x3ff888
  /home/bhalevy/.ccm/scylla-repository/local_tarball/libreloc/libseastar.so+0x36dea8
  /home/bhalevy/.ccm/scylla-repository/local_tarball/libreloc/libseastar.so+0x36d0e2
  0x101cefa
  0x105a390
  0x101bde7
  /home/bhalevy/.ccm/scylla-repository/local_tarball/libreloc/libc.so.6+0x27b89
  /home/bhalevy/.ccm/scylla-repository/local_tarball/libreloc/libc.so.6+0x27c4a
  0x101a764
```

Decoded:
```
~repair_service at ./repair/row_level.cc:3230
~shared_ptr_count_for at ././seastar/include/seastar/core/shared_ptr.hh:491
 (inlined by) ~shared_ptr_count_for at ././seastar/include/seastar/core/shared_ptr.hh:491
~shared_ptr at ././seastar/include/seastar/core/shared_ptr.hh:569
 (inlined by) seastar::shared_ptr<repair_service>::operator=(seastar::shared_ptr<repair_service>&&) at ././seastar/include/seastar/core/shared_ptr.hh:582
 (inlined by) seastar::shared_ptr<repair_service>::operator=(decltype(nullptr)) at ././seastar/include/seastar/core/shared_ptr.hh:588
 (inlined by) operator() at ././seastar/include/seastar/core/sharded.hh:727
 (inlined by) seastar::future<void> seastar::futurize<seastar::future<void> >::invoke<seastar::sharded<repair_service>::stop()::{lambda(seastar::future<void>)#1}::operator()(seastar::future<void>) const::{lambda(unsigned int)#1}::operator()(unsigned int) const::{lambda()#1}&>(seastar::sharded<repair_service>::stop()::{lambda(seastar::future<void>)#1}::operator()(seastar::future<void>) const::{lambda(unsigned int)#1}::operator()(unsigned int) const::{lambda()#1}&) at ././seastar/include/seastar/core/future.hh:2035
 (inlined by) seastar::futurize<std::invoke_result<seastar::sharded<repair_service>::stop()::{lambda(seastar::future<void>)#1}::operator()(seastar::future<void>) const::{lambda(unsigned int)#1}::operator()(unsigned int) const::{lambda()#1}>::type>::type seastar::smp::submit_to<seastar::sharded<repair_service>::stop()::{lambda(seastar::future<void>)#1}::operator()(seastar::future<void>) const::{lambda(unsigned int)#1}::operator()(unsigned int) const::{lambda()#1}>(unsigned int, seastar::smp_submit_to_options, seastar::sharded<repair_service>::stop()::{lambda(seastar::future<void>)#1}::operator()(seastar::future<void>) const::{lambda(unsigned int)#1}::operator()(unsigned int) const::{lambda()#1}&&) at ././seastar/include/seastar/core/smp.hh:367
seastar::futurize<std::invoke_result<seastar::sharded<repair_service>::stop()::{lambda(seastar::future<void>)#1}::operator()(seastar::future<void>) const::{lambda(unsigned int)#1}::operator()(unsigned int) const::{lambda()#1}>::type>::type seastar::smp::submit_to<seastar::sharded<repair_service>::stop()::{lambda(seastar::future<void>)#1}::operator()(seastar::future<void>) const::{lambda(unsigned int)#1}::operator()(unsigned int) const::{lambda()#1}>(unsigned int, seastar::sharded<repair_service>::stop()::{lambda(seastar::future<void>)#1}::operator()(seastar::future<void>) const::{lambda(unsigned int)#1}::operator()(unsigned int) const::{lambda()#1}&&) at ././seastar/include/seastar/core/smp.hh:394
 (inlined by) operator() at ././seastar/include/seastar/core/sharded.hh:725
 (inlined by) seastar::future<void> std::__invoke_impl<seastar::future<void>, seastar::sharded<repair_service>::stop()::{lambda(seastar::future<void>)#1}::operator()(seastar::future<void>) const::{lambda(unsigned int)#1}&, unsigned int>(std::__invoke_other, seastar::sharded<repair_service>::stop()::{lambda(seastar::future<void>)#1}::operator()(seastar::future<void>) const::{lambda(unsigned int)#1}&, unsigned int&&) at /usr/bin/../lib/gcc/x86_64-redhat-linux/13/../../../../include/c++/13/bits/invoke.h:61
 (inlined by) std::enable_if<is_invocable_r_v<seastar::future<void>, seastar::sharded<repair_service>::stop()::{lambda(seastar::future<void>)#1}::operator()(seastar::future<void>) const::{lambda(unsigned int)#1}&, unsigned int>, seastar::future<void> >::type std::__invoke_r<seastar::future<void>, seastar::sharded<repair_service>::stop()::{lambda(seastar::future<void>)#1}::operator()(seastar::future<void>) const::{lambda(unsigned int)#1}&, unsigned int>(seastar::sharded<repair_service>::stop()::{lambda(seastar::future<void>)#1}::operator()(seastar::future<void>) const::{lambda(unsigned int)#1}&, unsigned int&&) at /usr/bin/../lib/gcc/x86_64-redhat-linux/13/../../../../include/c++/13/bits/invoke.h:114
 (inlined by) std::_Function_handler<seastar::future<void> (unsigned int), seastar::sharded<repair_service>::stop()::{lambda(seastar::future<void>)#1}::operator()(seastar::future<void>) const::{lambda(unsigned int)#1}>::_M_invoke(std::_Any_data const&, unsigned int&&) at /usr/bin/../lib/gcc/x86_64-redhat-linux/13/../../../../include/c++/13/bits/std_function.h:290
```

FWIW, gdb crashed when opening the coredump.

This commit will help catch the issue earlier
when repair_service::stop() fails (and it must never fail)

Signed-off-by: Benny Halevy <[email protected]>

repair/row_level.cc

@@ -3218,13 +3218,22 @@ future<> repair_service::start() {
 }
 
 future<> repair_service::stop() {
+  try {
+    rlogger.debug("Stopping repair task module");
     co_await _repair_module->stop();
+    rlogger.debug("Waiting on load_history_done");
     co_await std::move(_load_history_done);
+    rlogger.debug("Uninitializing messaging service handlers");
     co_await uninit_ms_handlers();
     if (this_shard_id() == 0) {
+        rlogger.debug("Unregistering gossiper helper");
         co_await _gossiper.local().unregister_(_gossip_helper);
     }
     _stopped = true;
+    rlogger.info("Stopped repair_service");
+  } catch (...) {
+    on_fatal_internal_error(rlogger, format("Failed stopping repair_service: {}", std::current_exception()));
+  }
 }
 
 repair_service::~repair_service() {