Add a return after saving node power state

if successfully sync power state, we should just return 0 after node.save(),
but currently we have to go to next condition node.power_state == power_state

Change-Id: I49cc6e1b2dd957d4a60c611184cc640ca30773fa

ironic/conductor/manager.py

@@ -1986,6 +1986,7 @@ def do_sync_power_state(task, count):
                          {'node': node.uuid, 'state': power_state})
             node.power_state = power_state
             node.save()
+            return 0
 
     # If the node is now in the expected state, reset the counter
     # otherwise, if we've exceeded the retry limit, stop here