executor: fix the issue of coordinator.Close() taking too long (#50494)

close #50493

pkg/executor/internal/mpp/executor_with_retry.go

@@ -131,8 +131,10 @@ func (r *ExecutorWithRetry) Next(ctx context.Context) (resp kv.ResultSubset, err
 func (r *ExecutorWithRetry) Close() error {
 	r.mppErrRecovery.ResetHolder()
 	r.memTracker.Detach()
+	// Need to close coordinator before unregister to avoid coord.Close() takes too long.
+	err := r.coord.Close()
 	mppcoordmanager.InstanceMPPCoordinatorManager.Unregister(r.getCoordUniqueID())
-	return r.coord.Close()
+	return err
 }
 
 func (r *ExecutorWithRetry) setupMPPCoordinator(ctx context.Context, recoverying bool) ([]kv.KeyRange, error) {