message: cds: make log output more clear
  fixes
diff: @@ -49,13 +49,15 @@ void CdsApiImpl::parseResponse(const Http::Message& response) {
  for (auto& cluster : clusters) {
  std::string cluster_name = cluster->getString("name");
  clusters_to_remove.erase(cluster_name);
  + if (cm_.addOrUpdatePrimaryCluster(*cluster)) {
  log().info("cds: add/update cluster '{}'", cluster_name);
  - cm_.addOrUpdatePrimaryCluster(*cluster);
  + }
  }
  for (auto cluster : clusters_to_remove) {
  + if (cm_.removePrimaryCluster(cluster.first)) {
  log().info("cds: remove cluster '{}'", cluster.first);
  - cm_.removePrimaryCluster(cluster.first);
  + }
  }
  stats_.update_success_.inc();
  