Fix AddWidgetTest & AddWidgetConfigTest

Simplify the scrolling by a scroll down a smaller fixed distance. This
way we don't need to scroll back-n-forth in order to handle the
overlapping of the search bar and the targeted widget.

Test: run AddWidgetTest & AddWidgetConfigTest

Bug: 183616605
Change-Id: Icc72f4ba6c61bdb95ab5eaf22600407d59d14eba
2 files changed