message: cluster_manager_impl: Move comment to the right place.
  The placement of this comment has been bugging me for a while, might as well fix it.
diff: @@ -337,12 +337,12 @@ ClusterManagerImpl::httpConnPoolForCluster(const std::string& cluster, ResourceP
  ThreadLocalClusterManagerImpl& cluster_manager =
  tls_.getTyped<ThreadLocalClusterManagerImpl>(thread_local_slot_);
  - // Select a host and create a connection pool for it if it does not already exist.
  auto entry = cluster_manager.thread_local_clusters_.find(cluster);
  if (entry == cluster_manager.thread_local_clusters_.end()) {
  return nullptr;
  }
  + // Select a host and create a connection pool for it if it does not already exist.
  return entry->second->connPool(priority, context);
  }
  