Fix 5761: Power widget bar widens if >6 toggle buttons enabled

If more that 6 button widgets are enabled in the power widget, and hide scrollbar is active,
the space of the scrollbars is not recovered

This change make 2 modifications:
- Recreate the button layout, when a EXPANDED_HIDE_SCROLLBAR is received, instead of only update
the scrollview. This remove the scrollview if it is not needed.
- Move the setPadding of the buttonLayout to updateScrollbar to determine the correct botton padding

Change-Id: Ib8f149d9d220391ea0606da2252df4ace8cd7611