Settings: update time zone strings on date change

If the user changes the date, most obvious case being from 1970, to a
current date, and the user's selected Locale's country time zones have
been changed (according to ICU), we must update the time zone strings in
the system.

Ref: CYNGNOS-453

Signed-off-by: Roman Birg <roman@cyngn.com>
(cherry picked from commit 926c3b0a)

Change-Id: I487c54cd4f933286c5004d24a3f8730ee2d4e4f6
(cherry picked from commit d67600a4)