veyron/tools/mgmt: Hopefully fix TestV23NodeManager.

The old shell test used to check if the mtEP was empty but the new
integration tests do not.

Change-Id: If432d84c9c0e1b4c151f5c1d5b5f64747a55de9a
diff --git a/tools/mgmt/mgmt_v23_test.go b/tools/mgmt/mgmt_v23_test.go
index 0874d3d..f409e59 100644
--- a/tools/mgmt/mgmt_v23_test.go
+++ b/tools/mgmt/mgmt_v23_test.go
@@ -168,7 +168,7 @@
 		resolver := func() (interface{}, error) {
 			inv := namespaceBin.Start("resolve", name)
 			defer inv.Wait(nil, os.Stderr)
-			if r := strings.TrimRight(inv.Output(), "\n"); r != old {
+			if r := strings.TrimRight(inv.Output(), "\n"); len(r) > 0 && r != old {
 				return r, nil
 			}
 			return nil, nil