APN: Clean up mvno filtering of apn list

The current implementation was filtering out the mvnos correctly
but those apns ended up getting added to the end of the list rather
than alphabetically.  This patch keeps the sorting even for matching
mvno entries.

Change-Id: I4636a9be230834f093f9b21d69197fbf2449229c
TICKET: CYNGNOS-670
(cherry picked from commit acdfc53f)