Prevent AudioService dead lock issue.

Dead lock sequence:
 1. called onSetA2dpConnectionState()
  1-1. synchronized(mConnectedDevices)
 2. called onServiceDisconnected()
  2-1. synchronized(mA2DPAvrcpLock)
 3. waiting to lock(mConnectedDevices) in onServiceDisconnected()
 4. waiting to lock(mA2DPAvrcpLock) in onSetA2dpConnectionState()

========================================================================================
- watchdog issue
----- pid 3306 at 2014-10-14 16:15:12 -----
Cmd line: system_server

"main" prio=5 tid=1 MONITOR
  - waiting to lock <0x4343e9b0> (a java.util.HashMap) held by tid=46 (AudioService)
      at android.bluetooth.BluetoothA2dp$2.onServiceDisconnected(BluetoothA2dp.java:529)

"AudioService" prio=5 tid=46 MONITOR
      - waiting to lock <0x42ab7a58> (a java.lang.Object) held by tid=1 (main)
========================================================================================

Signed-off-by: Seunghwan Hong <seunghwan.hong@lge.com>

Change-Id: I99e061c07be01aabcd26786ef2ebb71f46717b93