BT: Audio: Enhance default BT application logging for Audio.

 - Make default logging for HeadsetStateMachine.
   state transitions, connection state changes etc.
 - Control verbose logging at runtime from adb shell.
 - Enable debug flag for A2DP and AVRCP.

CRs-Fixed: 601899

Conflicts:
	src/com/android/bluetooth/hfp/HeadsetStateMachine.java

Change-Id: I39eb8b31c29bd3616747181fe8a4540bdcbe7e76