resourcepolicyplugin: Emit resources released signal for acquiring resources as well.
qaudiooutput_pulse: Use custom volume if setVolume() was called.

Use custom volume if the argument value is within acceptable range.
Without this change if full volume (1.0) is requested, the volume is
never applied to the stream.
qaudiooutput_pulse: Return wanted for output's state.

Return m_wantedState here. We don't want to fool cautious users who
check the state before performing an operation into thinking an output
is already stopped and no further action is required only for it to come
alive again when resources become available.
qgstreamerplayercontrol: Remove unnecessary call to stopReleaseTimer().