Framework Base: Power Widget scrollbar not showed

If the number of the buttons in the Power Widget exceeded the LAYOUT_SCROLL_BUTTON_THRESHOLD
the HorizontalScrollView created is not showed because notification areas is over the scrollbar.
This occurs because buttons layout has set a bottom padding to not overlap the buttons. This has
sense in ics (where buttons has indicators), but not in jb there are not button indicator.
Remove the bottom padding to show the scrollbar. The scrollbar aspect is in tune with the rest of
the power widget

Change-Id: I1d1784a3b34329a2c710a2a3605f253f3756bf0b