base

Fixed AudioFlinger not always pausing tracks

If the pause request is received before the AudioTrack buffer was
completelly filled and the track ready for mixing, the pause is
not executed: the track just underruns and stays in pausing state.

The fix consists in considering the track ready for mixing immediately
if pausing.

Change-Id: Ia6cb4703fee2126e41011a6400ea8eeb3a3e5456