AudioService: fix lock ordering between BtHelper and AudioDeviceBroker

Make calls from BtHelper to AudioDeviceBroker that don't come
  from the AudioDeviceBroker event thread asynchronous

Bug: 123934346
Test: see bug
Change-Id: Id471141b3f5d9e481bf2e51c8ecd862c16b8d0cd
4 files changed