core (disco): use new client.server_jid property in getItems

sat/memory/disco.py

@@ -258,11 +258,10 @@ class Discovery(object):
         @param use_cache(bool): if True, use cached data if available
         @return: a Deferred which fire disco.DiscoItems
         """
-        server_jid = jid.JID(client.jid.host)
         if jid_ is None:
-            jid_ = server_jid
+            jid_ = client.server_jid
 
-        if jid_ == server_jid and not node:
+        if jid_ == client.server_jid and not node:
             # we cache items only for our own server and if node is not set
             try:
                 items = self.host.memory.getEntityData(