fix: Honor APT::Get::Purge setting when removing packages

Re mvo5#345

unattended-upgrade

@@ -1896,6 +1896,7 @@ def do_auto_remove(cache,             # type: UnattendedUpgradesCache
 
     pkgs_removed = []         # type: List[str]
     pkgs_kept_installed = []  # type: List[str]
+    purge = apt_pkg.config.find_b("APT::Get::Purge", False)
     if minimal_steps:
         for pkgname in auto_removable:
             if should_stop():
@@ -1904,7 +1905,7 @@ def do_auto_remove(cache,             # type: UnattendedUpgradesCache
             logging.debug("marking %s for removal" % pkgname)
             if pkgname in pkgs_removed:
                 continue
-            cache[pkgname].mark_delete()
+            cache[pkgname].mark_delete(purge)
             if not is_autoremove_valid(cache, pkgname, auto_removable):
                 # this situation can occur when removing newly unused packages
                 # would also remove old unused packages which are not set
@@ -1923,7 +1924,7 @@ def do_auto_remove(cache,             # type: UnattendedUpgradesCache
                 cache.clear()
     else:
         for pkgname in auto_removable:
-            cache[pkgname].mark_delete()
+            cache[pkgname].mark_delete(purge)
         if is_autoremove_valid(cache, "", auto_removable):
             # do it in one step
             if not dry_run: