Bluetooth: Create A2DP handler with looper

Found an exception due to A2dpHandler whenever Skype tries to load the
MediaPlayer to play Incomming Notification. Associated A2dp handler with
looper.

CRs-fixed: 452283
Change-Id: I73d3a5ff7728383e89da7252ea8db383014feab8
media: Locking mContext for message handler

 - mContext is used for broadcasting the intent which is done
   in message handler.
 - If the mContext is released from another thread before the
   message handler handles the message then there would be
   an exception
 - To avoid this have added syncronisation for all
   the messages so that the mContext is not released
   from any other thread before finishing the message handling

CRs-Fixed: 464905
Change-Id: Iaaec170181c11ff1dbb43f230a0dd3cf14c56d87
Merge "Bluetooth: Create A2DP handler with looper" into cm-10.1
Merge "media: Locking mContext for message handler" into cm-10.1