Synchronize Virtual Call, Voice Call and A2dp.

Use case:
1. Pair and connect MW600 BT headset.
2. Start A2DP streaming.
3. Make MO/MT call.
4. End call and verify if A2DP resumes on headset.

Failure:
After call ends, streaming resumes on Phone speaker
until headset is reconnected.

Root cause:
AVDTP still in START state when the call is active and
call indicators sent to headset

Fix:
Found some IOT issues where headsets behave abnormally if there is
START or SUSPEND over AVDTP in between call indicators sent for
Voip calls. This change will make sure A2dp is suspended before
sending call indicators and starts once the Virtual call is Ended.

Change-Id: Iead4bcd49a29ec544a6a0aa3b44423f01716fd01