message: server: more constness in server.cc
  Risk LeveL :low
  Testing: existing
  Doc Changes: n/a
  Release Notes: n/a
diff: @@ -510,8 +510,9 @@ RunHelper::RunHelper(Instance& instance, const Options& options, Event::Dispatch
  void InstanceImpl::run() {
  // RunHelper exists primarily to facilitate testing of how we respond to early shutdown during
  // startup (see RunHelperTest in server_test.cc).
  - auto run_helper = RunHelper(*this, options_, *dispatcher_, clusterManager(), access_log_manager_,
  - init_manager_, overloadManager(), [this] { startWorkers(); });
  + const auto run_helper =
  + RunHelper(*this, options_, *dispatcher_, clusterManager(), access_log_manager_, init_manager_,
  + overloadManager(), [this] { startWorkers(); });
  // Run the main dispatch loop waiting to exit.
  ENVOY_LOG(info, "starting main dispatch loop");
  @@ -598,7 +599,7 @@ InstanceImpl::registerCallback(Stage stage, StageCallbackWithCompletion callback
  void InstanceImpl::notifyCallbacksForStage(Stage stage, Event::PostCb completion_cb) {
  ASSERT(std::this_thread::get_id() == main_thread_id_);
  - auto it = stage_callbacks_.find(stage);
  + const auto it = stage_callbacks_.find(stage);
  if (it != stage_callbacks_.end()) {
  for (const StageCallback& callback : it->second) {
  callback();
  @@ -619,7 +620,7 @@ void InstanceImpl::notifyCallbacksForStage(Stage stage, Event::PostCb completion
  // worker threads have not been started so we need to skip notifications if envoy is shutdown
  // early before workers have started.
  if (workers_started_) {
  - auto it2 = stage_completable_callbacks_.find(stage);
  + const auto it2 = stage_completable_callbacks_.find(stage);
  if (it2 != stage_completable_callbacks_.end()) {
  ENVOY_LOG(info, "Notifying {} callback(s) with completion.", it2->second.size());
  for (const StageCallbackWithCompletion& callback : it2->second) {
  