AudioService: fix LE broadcast Audio volume update after calls

Align contextual volume update logic LE broadcast Audio when voice
call playback activity stops and starts.

Bug: 408976132
Bug: 422280166
Flag: EXEMPT bugfix
Test: Manual test
 1. connect BT turn LEA AUDIO, WIFI is on and connect one ap.
 2. Play music
 3. turn on brodcasrting,set password
 4. when listen music accpt a MT call aminute hung up the call

Change-Id: Ic32ed8f8cecf3536b78d1a8b8124ac07ec177b83