Fix issue with quick switch animation not running.

- We were intercepting touch before the quickscrub controller had a chance
  to handle the touch, which meant that we canceled the recents animation
  before passing the quick switch event to launcher.  Instead, just move
  the cancel recents animation logic to the key button view (before
  handling up) and ensure that we intercept from the button only in the
  cases we desire (a quick switch/scrub, recents animation start, or if
  it's a dock drag (not currently enabled).

Test: Fling on the nav button to quickswitch, ensure recents animation
      runs

Change-Id: Id89fda56f2996a38a9aea99179b5e2870b531003