fedora-live-base: Exclude sdubby from live installs
    
    systemd-boot is not yet supported on live media. Yet we
    want it to appear on images where anaconda is installing
    a system from RPMs (ex: the server dvd image).
    The fix for this problem at the moment is to exclude anaconda
    packages during the live media creation.
    
    Signed-off-by: Jeremy Linton <jeremy.linton@arm.com>