Treat the buffering state as playing

If the player bounces between buffering and playing there could be an
issue where the carkit retrieves the playback state and it is sent as
stopped even if AVRCP thinks its playing internally.

Bug: 79528664
Test: See in snooplogs that when playing music from the cloud, the
buffering state is sent as playing.

Change-Id: I7afb16af75b4f7f4f301b8f802a0084db25ff00b