verify networking setup in mdc for when dual stack enabled and nodes are on ovn

Luis passed by to let me know that they have made a change to networking in the ovn and the networking manager is now showing 3 again.

root@clusty-hajlypj2grjm-master-0:/var/home/core# cat /etc/NetworkManager/conf.d/95-cern-dhcp.conf 
[connection]
ipv6.addr-gen-mode=3
root@clusty-hajlypj2grjm-master-0:/var/home/core# nmcli -f ipv6.addr-gen-mode c show Wired\ connection\ 1 
ipv6.addr-gen-mode:                     default