Update Task surface position when bounds are changed

While adjusting the task bounds for ime, the new bounds and
display bounds were getting updated, but not "applied" to the
container surface. Lower level (eg. AppWindowToken) positions
are calculated relative to the Task, so without actually moving
the task surface, the position on screen was wrong.

Bug: 120775895
Test: open 2 apps in vertical split, open IME on bottom app.
      With IME open and 2 apps split visible, rotate screen
      to landscape. Also added TaskTests#testBounds to
      verify that setting bounds updates surface position.

Change-Id: Ib7443310bd5009278766d52a84874451dd1e04ed