AVRCP: Prevent concurrent access of Browser List

Concurrent access to mBrowsePlayerInfoList could happen still.

Test: none - concurrently change sessions and add a player?
Change-Id: Ibb2e1010eb1326387c04dae4ab2413d6aa3b2034
Bug: 37896665
(cherry picked from commit 5146bd27869df5473aa53e6271266f51733971ef)
1 file changed