Fix a small UI nit with screen reordering

-> When in overview mode, flinging the pages can leave the scroller
   running (invisibly) for much additional time, since the scroller
   fling bounds far exceed the alloawble scroll bounds (in order to
   achieve a hard wall type effect)
-> When this is happening, user couldn't pick up a page for reordering
-> Ended the scroller early in this case to avoid the problem

Change-Id: I8b6f140d9a87bb742e57625e90ca7d76a2158e28