Method stop

flow/Net2.actor.cpp:198–203

	void onMainThread(Promise<Void>&& signal, TaskPriority taskID) override;
	bool isOnMainThread() const override { return thread_network == this; }
	void stop() override {
		if (thread_network == this)
			stopImmediately();
		else
			onMainThreadVoid([this] { this->stopImmediately(); });
	}
	void addStopCallback(std::function<void()> fn) override {
		if (thread_network == this)
			stopCallbacks.emplace_back(std::move(fn));