mon/thrasher: set stopping

stopping was set by PR ceph#58282 to bool instead of set()

Fixes: https://tracker.ceph.com/issues/67496
Signed-off-by: Nitzan Mordechai <[email protected]>

Author: NitzanMordhai

qa/tasks/mon_thrash.py

@@ -161,7 +161,7 @@ def stop(self):
         """
         Stop the thrashing process.
         """
-        self.stopping = True
+        self.stopping.set()
 
     def join(self):
         """