message: In grpc_server_lib.cc initialize master_env_.collective_executor_mgr
  from the worker_env_ value.
diff: @@ -244,6 +244,7 @@ Status GrpcServer::Init(
  // Finish setting up master environment.
  master_env_.ops = OpRegistry::Global();
  master_env_.worker_cache = worker_cache;
  + master_env_.collective_executor_mgr = worker_env_.collective_executor_mgr;
  master_env_.master_session_factory =
  [config, stats_factory](
  SessionOptions options, const MasterEnv* env,
  