Don't IPC for every onPause() in NfcActivityManager.

The NfcService now contains additional code to make sure
that the registered NDEF callback corresponds to the package
running in the foreground. This allows us to stop calling
the NfcService on every onPause() to register the NDEF callback,
as NfcService itself will now detect that the app is no longer
in the foreground, and won't call the callback.

Bug: 5199662
Change-Id: Ibd0d21f8c7b76346238305a6684967263cb7d7e0