AVRCP: Only send the active player for media player listings

Some carkits will try to connect to the first player in the media player
list (Harman BMW) while other carkits will try to connect to the last player
in the listing (Magneti BMW). Send only one player in the listing so that
it doesn't matter if it connects to the first or the last.

Bug: 64991621
Bug: 64749777
Test: Connect to Harman BMW and see that the player listing only has one entry
      with multiple players installed, on Magneti carkit see that the carkit
      sets the current addressed player instead of a player that wasn't
      addressed

Change-Id: Ia8410473a5642bcc4ac7d1986c8c647fb7a4d78d
(cherry picked from commit 82cfeee4)