Use a ForwardingServiceListener in BluetoothVolumeControl

This pattern has been applied in https://r.android.com/2492537.
But it seems that this was not done for BluetoothVolumeControl.

Bug: 262605980
Test: atest BluetoothInstrumentationTests
Change-Id: I26339bed839a5b71dc3f2c98d2fec5098a1651ee