Merge "Unregistering PackageMonitor only when has registered it" am: 132f17ca3e am: 69d78722b5 am: ea9615522a am: 9f2f1e6dcb

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

Change-Id: Ib1dce6c544944dcd2e7ab83fad78494e5a4e8f53