Use lower similarity_level for some terminal wait_still_screens
    
    We can't use the default similarity_level for wait_still_screen
    when there's a flashing cursor - flashing cursor will always
    cause the similarity level to be too low and the wait will just
    time out at 30 seconds. Cut it to 42.
    
    Signed-off-by: Adam Williamson <awilliam@redhat.com>