plugin XEP-0045: fixed item-not-found exception when creating a room:

MAM was checked on the room itself, this patch changes it by checking the MUC service instead.

sat/plugins/plugin_xep_0045.py

@@ -968,7 +968,8 @@ class SatMUCClient(muc.MUCClient):
 
     @defer.inlineCallbacks
     def join(self, room_jid, nick, password=None):
-        has_mam = yield self.host.hasFeature(self.client, mam.NS_MAM, room_jid)
+        room_service = jid.JID(room_jid.host)
+        has_mam = yield self.host.hasFeature(self.client, mam.NS_MAM, room_service)
         if not self._mam or not has_mam:
             room = yield self._joinLegacy(self.client, room_jid, nick, password)
             defer.returnValue(room)