Loosen the user id check for master mute on automotive

For automotive,
- the car service is always running as system user
- foreground users are non-system users

Car service is in charge of dispatching the key event include master
mute to Android. Therefore, the getCurrentUser() is always different to
the foreground user.

See also go/aae-multi-user

Bug: 113268803
Test: adb shell input keyevent 164
Change-Id: I65d4a4bc1b96eec7dc61ed04c5acc425f37a9061