AudioService playback activity notif: check origin of player updates

When receiving updates about players, check the validity of the call:
 - the piid must be valid
 - the uid of the caller and that of the player must match

Test: adb shell dumpsys audio
Bug: 30955183
Change-Id: Id15e2b69764ed7db0b93e2c0c96472c30b1d2070