fb: unbreak recents animations on thumbnail click or dismiss recents screen

We load now correctly the recents screen and preload the first task on press
down off any key to get always recents without issues up. We cancel only
if any other key was pressed. I discovered during I am working on new recents
that this solves all issues but has one downside that if he user dismiss he recents
screen or click on one of the thumbnails to bring the choosen app to forground
that of course the last thumbnail is not cleared. Due that the entry animation
and some other things depent on what is currently preloaded we need to cancel
first task to have always in all cases the right animation.

Fix it with just calling cancelPreloadingFirstTask() if the user either
clicked on one of the thumbnails or dismissed the recents screen.

PS
- do the same when all thubmnails are swiped away
PS
- derp

Change-Id: I786c05d929f6a02b6d4928fc4a96aeb9a8e2d03e
SystemUI: Always show translucent decor on recents panel

Change-Id: Id3e371f841b065ba6ac7693d96b38504354b4fd9