Fixing several issues with accessibility

- Only reset the focused task if the task that we removed actually had 
  accessibility focus.
- Only reset the focused task on scroll if we are not in touch 
  exploration mode
- Ensure the focused view has accessibility focus when entering recents
  in touch exploration mode
- Instead of using the focused task, query for the accessibility focused
  task view when setting the focused task in response to the scroll 
  gesture.  In addition, use this accessibility focused task to 
  determine whether we need to add the accessibility actions
- No longer explicitly requesting accessibility focus on view focus
- Removing some unused code

Bug: 29046351
Change-Id: I5701a408bd919e47990f0d2fc6e4686eb9530d8e