Issue 49170 - sync plugin thread count not handled correctly
Bug Description: If sync repl connections get aborted the thread_count is
not properly updated which leads to the server hanging
on shutdown.
Fix Description: When connections get aborted we still need to shutdown
the result thread cleanly: remove the req, update thread
count, etc.
https://pagure.io/389-ds-base/issue/49170
Reviewed by: nhosoi(Thanks!)
(cherry picked from commit 770fcf4349ccf9e07ff0e1cf0d6991927ec9ba75)