[ldap-master/ldap-global] Swap alias and hostname between ldap-master and ldap-global

data/grid5000/sites/lille/servers/ldap-master.json

 {
   "alias": [
-    "ldap-master"
+    "ldap-global"
   ],
   "kind": "virtual",
   "network_adapters": {
@@ -9,5 +9,5 @@
     }
   },
   "type": "server",
-  "uid": "ldap-global"
+  "uid": "ldap-master"
 }
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