BluetoothAudioHAL: Wait for A2DP not playing if receiving A2dpSuspended=true

The Upper-layer may use A2dpSuspended=true parameter to inform of
stopping the A2DP playback and dropping streaming data before
establishing the SCO connection, and we have to wait for AVDTP
non-started. This helps prevent a race condition between A2DP and SCO.

Bug: 186613660
Bug: 185191975
Tag: #compatibility
Test: Making a MO / MT call manually while A2DP playing
Change-Id: I17ab9ef97b06928d092ae4bdaa697d97a5732bb0