No keyguard should be shown after reboot if it is in kiosk mode

1. we disable keyguard before KeyguardServiceDelegate connect the
   KeyGuardService and the request is ignored. We now remember the request
   and redo it after connected

2. Instead of checking PRIVATE_FLAG_KEYGUARD flag, use
   isKeyguardShowingAndNotOccluded to check is keyguard showing.

Bug: 28164604
Change-Id: Ib02b5fc9dcc6e8d9934309f1e540ece4d845363d