AVRCP: Don't use the queue for current metadata

If many requests come for the current metadata and the queue is large,
AVRCP could end up using a lot of CPU time. Instead just use the players
current metadata. Note this could lead to metadata sync issues as we
aren't using the same source for queue information and current song
information, but that should be reflected in the logs in case the issue
arrises.

Bug: 112563625
Test: runtest bluetooth
Change-Id: Ia95e20cb78e53e8efb1548dfd95ae9f8afcfd4b4