fedora-productimg-server is no more, don't try and install it
    
    This is breaking server image creation. **NOTE**: I don't know
    if it's correct to remove the whole <buildinstallpackages>
    block like this, or leave it there but empty - if we need to
    do the latter, I can adjust the PR.
    
    Signed-off-by: Adam Williamson <awilliam@redhat.com>