A2DP: Reduce Mutex lock scope of SetActive Device

Limit the scope of Mutex lock in SetActive device
to guard the access of A2DP SM and Active device
objects. Blocking AudioManager APIs are kept
outside critical section to avoid hitting long
monitor contention to ensure none of the related
threads (like AVRCP, A2DPService etc.) are blocked
due to blocking AudioManager calls.

CRs-Fixed: 2250237
Change-Id: I8ebdff14be72d5481d60e8e9a3e84db3bacf3e8a
1 file changed