Fix auto connection priority handling.

Bug: 3027023
1. user is connected to a headset. Headset is turned off.
2. User connects to another device. The priority of the first
   headset must be set to ON. We only have 1 device set at AUTO_CONNECT
   priority.

1. A remote headset sends an incoming connection. Don't set
   AUTO_CONNECT till its gets connected.
2. For outgoing connections, set it to AUTO_CONNECT in Connecting state
   since the user initated this connection.

Change-Id: Iaa211bf22b1fd99850875f7eda686c47142173ba