check for context canceled after competing for locks (#13239)

once we have competed for locks, verify if the
context is still valid - this is to ensure that
we do not start readdir() or read() calls on the
drives on canceled connections.

cmd/api-errors.go

@@ -1787,12 +1787,10 @@ func toAPIErrorCode(ctx context.Context, err error) (apiErr APIErrorCode) {
 
 	// Only return ErrClientDisconnected if the provided context is actually canceled.
 	// This way downstream context.Canceled will still report ErrOperationTimedOut
-	select {
-	case <-ctx.Done():
+	if contextCanceled(ctx) {
 		if ctx.Err() == context.Canceled {
 			return ErrClientDisconnected
 		}
-	default:
 	}
 
 	switch err {