Send USER_PRESENT for keyguard choice "None"

This enables sending ACTION_USER_PRESENT when the user has
selected "None" for their keyguard screen. When this happens,
we delegate sending the event to onScreenTurnedOn().

Tested:
- None -> sends broadcast in onSystemReady() the first time after boot
and in onScreenTurnedOn() there after.
- Slide -> sends broadcast only once when screen is dismissed
- Pattern -> sends broadcast only once when screen is dismissed

Fixes bug 7029707

Change-Id: I785c3255b15e2ee598a10d7d3580ba5c03dd0068