AVRCP Controller playback commands

When browsing ensure that play item command is still sent.  When
initiating playback request audio focus first.

Bug: 131174820
Test: release audio focus, send a command via media session that would
begin playback, verify audio begins playing.

Change-Id: I72d4e344db5a45176af944ccbd983fee47b1fc5d
Merged-In: I72d4e344db5a45176af944ccbd983fee47b1fc5d