JACK: Add locking to disconnect cleanup
JACK: Add locking to disconnect cleanup

jack_disconnect() is supposed to stop callbacks towards
to the client, but to err on the safe side, protect
the final cleanup steps with a mutex.

jeremysalwen/Ecasound-LV2,jeremysalwen/Ecasound-LV2,jeremysalwen/Ecasound-LV2,jeremysalwen/Ecasound-LV2,jeremysalwen/Ecasound-LV2