livesys-gnome: Neuter auth dialog when starting live installer
    
    anaconda is going to start using polkit instead of consolehelper
    to elevate the user to root.
    
    gnome-shell requires the user confirm any polkit connversations,
    even if they don't require authentication. That make sense
    for some use cases, but not here.
    
    This commit side steps that issue by creating a rule to skip the
    conversation entirely.