Fix bug 2329540

 Part 1 of the fix: when the user doesn't elect to use the car dock
 for music and media, the APM was not aware of the device being
 docked.
 This is fixed by dissociating the notification for the APM of
 the docking to the dock from the sink state change of the A2DP
 device.
 Also missing was forcing the volumes to be reevaluated whenever
 the device is docked or undocked, as volumes for docks may
 differ, even when the same output device is being used.

Change-Id: If5314e27821a71adbd6df6fdf887c45208241d96