[lille] Add lbertot-vm persistent VM

data/grid5000/sites/lille/servers/lbertot-vm.json

+{
+  "expire": "2021-10",
+  "kind": "virtual",
+  "network_adapters": {
+    "default": {
+      "ip": "172.16.45.14"
+    }
+  },
+  "type": "server",
+  "uid": "lbertot-vm"
+}
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