Fix DNS config in realmd_join_sssd and realmd_join_cockpit
    
    Seems what they had before worked until systemd-resolved became
    the default; now we need to make sure we do nmcli mod and then
    bring the connection down and up, as we do in tapnet.pm. Writing
    to resolv.conf is kinda "wrong" for resolved but I don't think
    it really breaks anything so I think I'll just leave those bits
    in until F32 goes EOL just in case they're still somehow needed
    on F31 or F32.
    
    Signed-off-by: Adam Williamson <awilliam@redhat.com>