Tests: Add test for updateValueWhileDragging property (Slider)
Tests: Add test for updateValueWhileDragging property (Slider)

Change-Id: I8650cb02f0db261462ebec816e80ec5c89fec8a7
Reviewed-by: Liang Qi <0f3d3d9587f4f01263b2640b7eef7a92a160ec94@digia.com>

drgvond/qtquickcontrols,kobolabs/qtquickcontrols,kobolabs/qtquickcontrols,mizukusak/qtquickcontrols,mizukusak/qtquickcontrols,richardmg/qtcomponents,drgvond/qtquickcontrols,kobolabs/qtquickcontrols,mizukusak/qtquickcontrols,drgvond/qtquickcontrols,richardmg/qtcomponents,richardmg/qtcomponents