Handle Firefox 100 disappearing scrollbars in Cockpit update test
    
    The Cockpit update test relies on scrolling the Cockpit left bar
    to find the Software Updates page, but in Firefox 100, the scroll
    bars disappear shortly after the last time you moved the mouse.
    To deal with this, instead of looking for a scroll bar to scroll,
    we'll click the search box in the left bar and hit 'up' to scroll
    it to the bottom.
    
    Signed-off-by: Adam Williamson <awilliam@redhat.com>