[bug 14208] Remove ganglia.

Related to bug 14208.

This merge request remove ganglia's virtual machines from the ref-repo.

data/grid5000/sites/grenoble/servers/ganglia.json

-{
-  "kind": "virtual",
-  "network_adapters": {
-    "default": {
-      "ip": "172.16.31.111"
-    }
-  },
-  "type": "server",
-  "uid": "ganglia"
-}
\ No newline at end of file