[BT] Fix not able to select A2DP as the output

[Description]
BT set a2dp active device is null when
the wired headset is connected.
But it can’t set to native layer due to bd_addr is null.

After unplugging the wired headset,
since the native layer determines that
the active device has not changed.
Pressing the play button on the headset
will not trigger the active flow.

Fix Cannot remove active device in native layer.

Bug: 177190233
Tag: #compatibility
Test: 1. A2DP Source: PASS
      2. AVRCP Target: PASS

Change-Id: I096782a9fb248829dedcdc1c6e592bfd75c63798