KeyGuard: minimize challenge when showing the lockscreen (1/2)

This will allow the user to choose wether the lockscreen
challenge (circle, pattern, pin) is minimized when the screen
is turned on.

Change-Id: Ib6f3cde5f2f951b42a9e8a0b5897ace864c4f6c3
Signed-off-by: Dirk Rettschlag <dirk.rettschlag@gmail.com>
Merge "KeyGuard: minimize challenge when showing the lockscreen (1/2)" into kitkat