core: maintain a stop list for prepared, playing or completed sinks.
core: maintain a stop list for prepared, playing or completed sinks.

we need to stop only active sinks which are preparing, prepared, playing
or completed. this is done when the request completes or failure occurs
during sink preparation.

jusa/ngfd,jusa/ngfd,android-808/ngfd,android-808/ngfd,jusa/ngfd