Prevent fighting of setting scroll position property by ItemView and ScrollBar

Prevent fighting of setting scroll position property by ItemView and ScrollBar

[problem]      When ItemView is still scrolling, touch and drag the fast scroll bar,
               the fast scroll bar is not responsive for some time and ItemView scrolls
               to the wrong position sometimes.
[cause]        When scroll position property is being animated by ItemView, if something
               else (e.g. ScrollBar) tries to modify the scroll position property at the
               same time, there is a fighting of setting the same property between the two.
[solution]     Cancel scroll animation when it is in fast scroll mode.

Change-Id: I3de03d7b21b929fe527b907e58464896b774c489
Signed-off-by: Adeel Kazmi <adeel.kazmi@samsung.com>