GsmSST: Disregard any invalid verbose values for timezones in NITZ requests

And assume anything resulting in "GMT" is invalid, since that's the
default value returned by libcore

Change-Id: Iee8509c76228f9977b5df3f4e69c82ca063efce8
Merge remote-tracking branch 'omni/android-4.4' into omni-4.4