Add a new priority for Auto Connection of A2DP.

Add a new priority for Auto Connection of A2DP.

1. PRIORITY_OFF is when user unchecks A2DP connection profile box.
2. By default, when you bond, it will be PRIORITY_ON.
3. When the profile gets connected, the priority gets set to
   PRIORITY_AUTO_CONNECT. This means that we will connect
   automatically to this profile.
4. When the user disconnects, we downgrade the priority to PRIORITY_ON,
   which means we won't reconnect automatically.

a) We need to make a similar change to Handsfree profile.
b) We need to rework the profile management design and code which
  will fix the 6 second timer that we have for A2DP reconnection.