message: fixed dns async resovler bugs.
diff: @@ -227,8 +227,8 @@ static int swDNSResolver_onReceive(swReactor *reactor, swEvent *event)
  char key[1024];
  int request_id = ntohs(header->id);
  - int n = snprintf(key, sizeof(key), "%s-%d", _domain_name, request_id);
  - swDNS_lookup_request *request = swHashMap_find(request_map, key, n);
  + int key_len = snprintf(key, sizeof(key), "%s-%d", _domain_name, request_id);
  + swDNS_lookup_request *request = swHashMap_find(request_map, key, key_len);
  if (request == NULL)
  {
  swWarn("bad response, request_id=%d.", request_id);
  @@ -254,7 +254,7 @@ static int swDNSResolver_onReceive(swReactor *reactor, swEvent *event)
  }
  request->callback(request->domain, &result, request->data);
  - swHashMap_del_int(request_map, request_id);
  + swHashMap_del(request_map, key, key_len);
  sw_strdup_free(request->domain);
  sw_free(request);
  