Add a check that correct filesystem was used on Server installs
    
    This is currently broken, but openQA doesn't notice; we really
    should. We could also check the default in other cases, but I
    think that's less clear-cut, as it's kind of an anaconda design
    choice, it's not mandated in Fedora requirements anywhere.
    
    Signed-off-by: Adam Williamson <awilliam@redhat.com>