Merge "[Ongoing Call] Always unregister the UidObserver." into sc-dev am: 3d1c180320 am: 35c1997024

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/15503430

Change-Id: Icee3b7e5e5c6823faa6fdf7916d81dd580d73646