plugin XEP-0313: don't wait for MAM to be retrieved in connection workflow:

MAM retrieval can be long, and can be done after connection, message just need to be
sorted when being inserted (i.e. frontends must do insort).
To avoid blocking connection for too long and result in bad UX and timeout risk, one2one
MAM message are not retrieved in background.

sat/plugins/plugin_xep_0313.py

@@ -159,8 +159,8 @@ class XEP_0313(object):
             log.info(_("We have received {num_mess} message(s) while offline.")
                 .format(num_mess=count))
 
-    async def profileConnected(self, client):
-        await self.resume(client)
+    def profileConnected(self, client):
+        defer.ensureDeferred(self.resume(client))
 
     def getHandler(self, client):
         mam_client = client._mam = SatMAMClient(self)