fix not return when channel closed

Signed-off-by: kerthcet <kerthcet@gmail.com>

cluster/images/etcd-version-monitor/etcd-version-monitor.go

@@ -251,6 +251,7 @@ func getVersionPeriodically(stopCh <-chan struct{}) {
 		}
 		select {
 		case <-stopCh:
+			return
 		case <-time.After(scrapeTimeout):
 		}
 	}