Suppress Registration Errors when WFC disabled

There is still the possibility of IMS registration
failing for a time after the user has disabled WFC.
This causes registration error messages
to keep popping up. This change suppresses
those notifications when the WFC setting is off.

Bug: 64412124
Test: Manual
Change-Id: I5c0b4531655bed57e5a8efe0ebffe13a027e597f