Fix NPE when apns list is null. Probably just side-effect of another error.

Change-Id: Ib1f0296a56c7ba0b5eacc2d85fc73ada6c19d8f2
UNINITIALIZED and UNKNOWN are ambiguous descriptors for mMncLength.
I'm betting one or both got used interchangably by accident, thus introducing a bug.
Check for either case throughout. This seems to make connecting to data service
on the Motorola Droid 4 (Verizon) more reliable.

Change-Id: I42562aa26487c97b7c5654ea73cad9c486544198