Return no track selected if no track is currently selected.

Fix to satisfy AVRCP 1.4 spec.
In EVENT_TRACK_CHANGED response request,
if a track is selected , then return 0x0 in the response.
if no track currently selected,then return 0xFFFFFFFFFFFFFFFF in the INTERIN response.

Bug: 22519285

Change-Id: Iaaae1d4acf918049d99c27d9ad98bde15242ade1