_graphical_input: retry launch of keyboard if it fails
    
    First attempt at this often fails for some reason - while we're
    typing 'keyboard' the results come up as normal, but before we
    hit enter, they all disappear and are replaced with "no results
    found" (in Japanese). Dunno why. This will hopefully work around
    that, if it works reliably on the second try.
    
    Signed-off-by: Adam Williamson <awilliam@redhat.com>