Ensured scrolling would not be interrupted by other controls

When the `HorizontalListview` is added to a vertically scrolling page, the scrolling can very easily get interrupted. This is because the vertical scroller will start scrolling as soon as touch movement is going in a vertical direction. 

`RequestDisallowInterceptTouchEvent(true)` is now called as soon as the `HorizontalListview` starts scrolling, to prevent any other controls from intercepting touch events for as long as the user is scrolling.