Keep krunner results view top aligned

The workflow is:
 - results change
 - we wait for a frame
 - listview updates and resiszes
 - this changes the contentHeight
 - the main layout polish event runs
 - this does a re-layout and updates the implicitHeight
- the relayout is agains the current window size, if the listview
shrinks this means it adds space above and below
 - we draw the window content before layout polishes again

Setting a vertical alignment in the layout won't do anything, that never
adjusts space around the layout item. A spacer works better.