If jackd changes the buffer size or sample rate, jackaudiosink hangs
and can't be stopped. This also happens if jack is configured as slave
and a gstreamer pipeline is started on the slave machine while the jack
master isn't running yet. If the the jack master is started it changes
the buffer size / sample rate and jackaudiosink can't be stopped.
This fix calls jack_shutdown_cb when jack_sample_rate_cb or
jack_buffer_size_cb is called.
https://bugzilla.gnome.org/show_bug.cgi?id=771272
1215849e69