Fixed unnecessary tear down

1. Register RAT/registration state changed event
   from service state tracker will not trigger
   sending changed event to all registrants anymore.
2. When building waiting APNs to reevalulate if tearing
   down is needed or not, will check if the APN setting
   from the current data connection is one of the APN
   setting in the new list. If yes, will not tear down
   the data connection.

Fix: 150818730
Test: Unit tests + telephony sanity tests
Change-Id: I7015ba147534fe0dd8feb3ac7a068f3138ece399