A2dpSink: Enable Absolute volume feature for Sink.

- As part of aosp refactoring absolute volume has been broken.
  So, enabled absolute volume feature.

- While removing setactivedevice, it should be out of mBtA2dpLock
  scope. So, that btif events has been processed without any lag.

CRs-Fixed: 2469398
Change-Id: Ic92b40a75eb18ba79c17947c14df206c7c5fae8a
3 files changed