Fix views not being visible on Recents Go.

If we bind the loading task views but then on the tasks being loaded
realize there are no items, it's possible to animate from the empty
content view to the regular content view and then back. Currently, this
leads to updateContentView not being called properly the second time
since both views are still visible during the animation, so this CL
fixes that and cancels any on-going crossfade animations.

Bug: 114136250
Fixes: 130580680
Test: Remove last item from recents, go to recents again, empty view
shown
Change-Id: If1a4caab15f9b6d7ccd3abbc06f5866e06650db8
(cherry picked from commit cce954f3)