private/testplanet: Use config with name set when empty

In testplanet Run function we create a new configuration variable on
each t.Run for setting the value to the config name field when it's
empty, however the new copy of the configuration was not used.

Change-Id: I9da34e743f9648850c96556eab0349e742db3aac

private/testplanet/run.go

@@ -52,7 +52,7 @@ func Run(t *testing.T, config Config, test func(t *testing.T, ctx *testcontext.C
 				planetConfig.Name = t.Name()
 			}
 
-			planet, err := NewCustom(zaptest.NewLogger(t), config, satelliteDB)
+			planet, err := NewCustom(zaptest.NewLogger(t), planetConfig, satelliteDB)
 			if err != nil {
 				t.Fatalf("%+v", err)
 			}