Method task_loop_once

tee/cocoon/pow.cpp:195–198

  }

  td::actor::Task<Action> task_loop_once() override {
    co_await do_loop();
    co_return state_ == State::Done ? Action::Finish : Action::KeepRunning;
  }

  td::actor::Task<td::SocketPipe> finish(td::Status status) override {
    co_await std::move(status);