[toulouse][gw] Add 'gw' alias.

data/grid5000/sites/toulouse/network_equipments/gw-toulouse.json

 {
+  "alias": [
+    "gw"
+  ],
   "ip": "172.17.127.254",
   "ip6": "2001:660:4406:900::ffff:ffff",
   "kind": "router",

input/grid5000/sites/toulouse/networks/gw-toulouse.yaml

@@ -2,6 +2,8 @@
 gw-toulouse:
   model: Temporary-Dell-OS6
   serial: unknown
+  alias:
+    - gw
   ip: 172.17.127.254
   ip6: 2001:660:4406:900::ffff:ffff
   kind: router