Skip tracking clients OOM test when I/O threads are enabled (valkey-i…

…o#764)

Fix feedback loop in key eviction with tracking clients when using I/O
threads.

Current issue:
Evicting keys while tracking clients or key space-notification exist
creates a feedback loop when using I/O threads:

While evicting keys we send tracking async writes to I/O threads,
preventing immediate release of tracking clients' COB memory
consumption.

Before the I/O thread finishes its write, we recheck used_memory, which
now includes the tracking clients' COB and thus continue to evict more
keys.

**Fix:**
We will skip the test for now while IO threads are active. We may
consider avoiding sending writes in `processPendingWrites` to I/O
threads for tracking clients when we are out of memory.

---------

Signed-off-by: Uri Yagelnik <[email protected]>
Signed-off-by: Madelyn Olson <[email protected]>
Co-authored-by: Madelyn Olson <[email protected]>
Signed-off-by: Ping Xie <[email protected]>

tests/support/server.tcl

@@ -241,6 +241,11 @@ proc tags_acceptable {tags err_return} {
         return 0
     }
 
+    if {$::io_threads && [lsearch $tags "io-threads:skip"] >= 0} {
+        set err "Not supported in io-threads mode"
+        return 0
+    }
+
     if {$::tcl_version < 8.6 && [lsearch $tags "ipv6"] >= 0} {
         set err "TCL version is too low and does not support this"
         return 0