End scroller if it has already reached the final position

- The system overscroller seems to take a long time to settle even
  after the final position has been reached, so if that has already
  happened and there is no edge effect, then just end the scroller.
- Remove unused code related to SmoothPageView

Bug: 184983443
Test: Quickswitch and ensure we finish the recents animation after it settles
Change-Id: I9fa72ddd6b6e0d38b6f622c776a2ac5f5b055760