Let avahi handle mdns requests
    
    We need to disable it by default in resolved so that it doesn't fight
    with avahi for the port when both are started up in parallel.
    
    I also moved nss-files before nss-resolve. This is unfortunate because
    resolved cached files and with the move, the file will be re-read on each
    query. Nevertheless, we want nss-files to have higher priority than nss-mdns
    to honour local config. Fortunately, only some people put lots of entries
    in /etc/hosts, so the inefficiency incurred by this isn't important for
    most users.
    
    nss-myhostname is moved after nss-files, following the change in
    upstream recommendations.