Fixing various layout issues when docking

- Fixing regression where we were scrolling to front immediately on 
  dragging-to-dock a task, we should only scroll to the front on 
  configuration change.
- Accounting for the inset when calculating the final stack bounds
  (similar to b/27921362)
- Fixing issue with task views being clipped as user drags a view due 
  to the bounds of the view changing.  We manually now set the frame on
  the view to the current stack task bounds.
- Simplifying calls to animate the task view bounds
- Removing old instance state code

Change-Id: I17d3e33e159ff250c11a504ef87558051926a974