Ensure Flickable bounds detection is executed at the end of animation.

In pixelAligned mode the content position when animating is rounded to
a whole pixel, so the contentItem may reach the bound before the
animation completes.

Ensure bounds detection is run on animation completion.

Task-number: QTBUG-36300
Change-Id: I083ff6a03a5d1b9ca9e2201487b602f1588002be
Reviewed-by: Robin Burchell <robin+qt@viroteck.net>
Reviewed-by: Joona Petrell <joona.petrell@jollamobile.com>