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: I361650400e71976d8327ee3929947ca26a9eff57
Merge "GsmSST: Disregard any invalid verbose values for timezones in NITZ requests" into cm-10.2