fix(disco): avoid autoping warning on disco#info responses from users

The autoping availability warning should only trigger for disco#info
responses from the XMPP server (no 'from' attribute), otherwise the
warning message is displayed excessive amount of times.

Refs #80

src/xmpp/iq.c

@@ -2430,7 +2430,10 @@ _disco_info_response_id_handler_onconnect(xmpp_stanza_t* const stanza, void* con
             }
             child = xmpp_stanza_get_next(child);
         }
-        _disco_autoping_warning_message(features);
+
+        if (!from) {
+            _disco_autoping_warning_message(features);
+        }
     }
 
     connection_features_received(from);