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

Should fix CYAN-2271

Change-Id: I361650400e71976d8327ee3929947ca26a9eff57
Merge remote-tracking branch 'cyanogen/cm-10.1' into cm-10.1