Dismiss or cancel in SwipeDismissLayout on screen off.

Fix for situation where you palm the device while swiping away an
ambiactive activity (or rather, when you swipe slightly an ambiactive
activity during palm gesture). This would make the activity stay in half
dismissed state. Instead when the screen goes off, we either dismiss or
cancel the dismissal.

Change-Id: I82e699c00c25bc97dd95bc6473a17e5817f7667a