SDK / exoplayer

This works around an issue the audio track continues to play audio data written
after calling AudioTrack.pause(), which breaks rebuffering behavior (as video
can never catch up if audio continues to be consumed, in some circumstances).

Also don't increment the timestamp wrap count if the track is paused, to work
around an issue where the playback head position jumps back to zero after the
AudioTrack position jumps back to zero.