Ensure app op restrictions reset when the app that set them dies.

We were not keeping track when an app that set an app op restriction
dies to clean up after that. As a result we may end up with stale
restrictions that will be there until the device reoots - not cool.
This change adds remote binder death tracking and simplifies the
code as adding the formed would have made more complex.

bug:28770536

Change-Id: I7dcaafba2354843a0cdf0206ab1f96625edc5120