SystemUI: Fix prompt message is wrong in pattern unlock mode issue

The value of config_max_unlock_countdown_times control whether support
countdown counts or not, should judge it before get the prompt message.
The function of countdown counts isn't complete, it doesn't support
factory data reset yet.

Judge the value of config_max_unlock_countdown_times before show the
prompt message.
Improve the factory data reset function.

CRs-Fixed: 768890

Change-Id: Id0081e7ebea7526ff02f8c730920e1efc106a24a