fix TCP unregister systematically fails

[Houston4444]

Hi. The OSC TCP /unregister method systematically fails, because code compares the url argument to the saved hostname.

This method is used by carla-control, it means that it is not possible to stop carla-control, restart it and register again to the same carla instance.

This PR fixes the problem of course.

I need it because I use a self made TCP server connected to Carla to save/restore my presets.