Reset RecentsView#mNextPage when swiping to home

This ensures that we don't inadvertently update mCurrentPage to be
mNextPage in computeScrollHelper(), which would in turn mess up
calculations such as RecentsView#getHorizontalOffsetSize().

Also removed resetNextPage parameter from forceFinishScroller(), as
resetNextPage was always passed as true anyway.

Test: Swipe up and to the right to home, ensure adjacent page goes all
the way off screen
Fixes: 199927699

Change-Id: Iee1ffac10e5195f0c3a124a23b06d5411ecd7ba2