Scroll inertia slows down unnaturally when scrolling up back towards image.

[hokster7]

Reproduction:

1. Show an image as a top view controller.
2. Display at least of a couple of screenfuls of content. Scroll to the bottom.
3. Flick down to scroll up. Standard scrollview deceleration takes 2-3 seconds to bring the scrolling to a stop.
4. Observe that deceleration is much stronger when the scrollview hits the image; scrolling stops much more abruptly, and usually doesn't reach the top of the image.