Set device volume when AudioManager says device is connected

Instead of setting the remembered volume before the active device switch
happens, set it once we get a callback from the AudioManager that the
device has changed. This prevents the posibility of the new volume being
used with the old active device.

Bug: 79529581
Test: Switch devices multiple times and see that the volume changes when
the new device is connected.

Change-Id: I6a9e10654c844a5e2727d5409e27dd9e8176dd18