Use defer style to stop tickers to avoid current/possible misuse (#5883)

This commit ensures that all tickers are stopped using defer ticker.Stop()
style. This will also fix one bug seen when a client starts to listen to
event notifications and that case will result a leak in tickers.

cmd/fs-v1-multipart.go

@@ -714,11 +714,11 @@ func (fs *FSObjects) AbortMultipartUpload(ctx context.Context, bucket, object, u
 // blocking and should be run in a go-routine.
 func (fs *FSObjects) cleanupStaleMultipartUploads(ctx context.Context, cleanupInterval, expiry time.Duration, doneCh chan struct{}) {
 	ticker := time.NewTicker(cleanupInterval)
+	defer ticker.Stop()
+
 	for {
 		select {
 		case <-doneCh:
-			// Stop the timer.
-			ticker.Stop()
 			return
 		case <-ticker.C:
 			now := time.Now()