Adjust mirrordb NFS mount for v4
    
    Use relative path (server side export uses fsid=0) to work
    with the new default of NFSv4.
    Additionally, swap the lines to be both alphabetical and more
    logical ("from" -> "to").
    
    Signed-off-by: Georg Pfuetzenreuter <mail@georg-pfuetzenreuter.net>