audio policy: wait for mute during a2dp codec reconfiguration

When the a2dp codec reconfiguration requires switching between the
primary and Bluetooth HALs and we mute and unmute the media strategy,
make sure the muted audio has time to propagate down the audio path
before triggering the Bluetooth device disconnection.

Bug: 333001142
Test: repro steps in bug
Change-Id: Idcd928777f4905c4367183b9cd2716d6972d954f