Reset counter if background pool is full

src/Storages/MergeTree/BackgroundJobsExecutor.cpp

@@ -58,6 +58,7 @@ void IBackgroundJobExecutor::scheduleTask(bool with_backoff)
     }
     else
     {
+        no_work_done_count = 0; /// We have work, but run without backoff
         next_time_to_execute = 1000 * sleep_settings.thread_sleep_seconds_if_nothing_to_do;
     }