Fixing issue with task animating from 0,0.

- When we get all the initial task transforms when swiping to dismiss, 
  the tasks that are not visible at the original scroll position but are
  in the final position are not initialized correctly.  Instead when
  getting the current transforms for all tasks, always calculate their 
  transforms regardless of whether they are currently visible or not.
- This revealed another issue where on snap-back, a task that was 
  visible at the new scroll and not at the old scroll was not getting 
  removed until the next update (which would cause a task view to linger
  if you press home for example).

Bug: 26964326
Change-Id: I4db9cd1b072d3841351c2e84b219ca224a3045f9