[nancy][server][viabaca] Add Viabaca VM description

data/grid5000/sites/nancy/servers/viabaca.json

+{
+  "kind": "virtual",
+  "network_adapters": {
+    "default": {
+      "ip": "172.16.79.136"
+    }
+  },
+  "type": "server",
+  "uid": "viabaca"
+}
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