message: Check that the model didn't change when reloading a flag file
diff: @@ -295,7 +295,12 @@ class SelfPlayer {
  {
  absl::MutexLock lock(&mutex_);
  + auto old_model = FLAGS_model;
  MaybeReloadFlags();
  + MG_CHECK(old_model == FLAGS_model)
  + << "Manually changing the model during selfplay is not supported. "
  + "Use --checkpoint_dir and --engine=remote to perform inference "
  + "using the most recent checkpoint from training.";
  game_options.Init(thread_id);
  player = absl::make_unique<MctsPlayer>(dual_net_factory_->New(),
  game_options.player_options);
  