Merge "Unregistering PackageMonitor only when has registered it" am: 132f17ca3e am: 69d78722b5 am: ea9615522a

Original change: https://android-review.googlesource.com/c/platform/frameworks/base/+/1456123

Change-Id: I7c75f05b97286054dd25c92a20b5ab97162c40c7