BT: Absolute Volume feature should be enabled only for A2dp device.

Absolute Volume feature should be enabled only for device which
supports A2DP Sink and AVRCP. This change will make sure this
feature is not enabled for only AVRCP supported devices.

CRs-fixed: 582262
Change-Id: I75509d0b0fd1b06fa08390940a327dd2887d7562
Bluetooth: A2DP SINK audio focus and state handling changes

 - handle audio concurrencies
 - handle resume stream in A2DP SINK

CRs-Fixed: 584276

Change-Id: I24b0644ba552d5ebaad9a371aa6ae42fcfddee49
Bluetooth: Re-start sniff timer on Signalling connection.

On ACL disconnect switch to idle state if DUT is in
opening state.
Start/Stop sniff timer based on signalling channel
connection / disconnection.

CRs-Fixed: 590614

Change-Id: Ic3f268703067155ffd55a43f320ce199641c6b3f