[nancy][grue] Add IPv6 for grue custer

data/grid5000/sites/nancy/clusters/grue/nodes/grue-1.json

@@ -94,6 +94,7 @@
       "firmware_version": "7.10 0x8000519f 19.0.12",
       "interface": "Ethernet",
       "ip": "172.16.77.1",
+      "ip6": "2001:660:4406:500:2::1",
       "kavlan": true,
       "mac": "e4:43:4b:a5:71:dc",
       "management": false,