(ScrollView) Panning is disabled if ScrollTo is called while panning
[problem] If application calls ScrollTo while we're panning we go into an incorrect state.
[cause] When we're panning, and the application calls ScrollTo, swiftly followed by a call
to disable scroll-sensitivity, the panning value is never cleared.
When scroll-sensitivity is enabled, we start animating to a wrong position.
Also trying to use the property value when we set sensitivity which can be out-of-date.
[solution] Clear the panning value when we want to animate to another position.
Use event-side panning value when changing scroll-sensitivity.
Change-Id: I3cc2200839ad3a2ec1fc705f542bd8df41502462
Signed-off-by: Adeel Kazmi <adeel.kazmi@samsung.com>