Multi-A2DP: stop or flush the A2DP queue only for Active peer

The A2DP queue should be flushed or the A2DP Tx/Rx operations
should be stopped only for the Active peer.
Otherwise, disconnecting a non-active A2DP Peer stops audio
output for the Active peer.

Bug: 73956686
Test: Manual: Connect two A2DP Sink devices, play music on the
      Active device, disconnect the non-Active device
Change-Id: I32a624c012ef2cd9ef0057f7289a6ed713f88039