AVRCP getConnectedDevices

Utilize the same connectedDevice list rather than asking the
avrcpService for the list multiple times possibly yielding different
lists.

Bug: 63103934
Test: Insert delays and disconnect BT while in the middle of sending
play/pause commands.

Change-Id: Ib6016d853cf1e7e72923df851e7a17752bfee07d
Merged-In: I85b6ce47b1724557b298c54e0a73bef8849ac3ba
(cherry picked from commit 673e4dc3)