message: tperf: schedule timer just once
  Summary:
  The current implementation re-schedules the timer on receiving a new stream.
  If the peer keeps creating new streams the connection is never closed.
  (Note: this ignores all push blocking failures!)
diff: @@ -312,7 +312,10 @@ class TPerfClient : public quic::QuicSocket::ConnectionCallback,
  void onNewUnidirectionalStream(quic::StreamId id) noexcept override {
  LOG(INFO) << "TPerfClient: new unidirectional stream=" << id;
  + if (!timerScheduled_) {
  + timerScheduled_ = true;
  eventBase_.timer().scheduleTimeout(this, duration_);
  + }
  quicClient_->setReadCallback(id, this);
  }
  @@ -390,6 +393,7 @@ class TPerfClient : public quic::QuicSocket::ConnectionCallback,
  ~TPerfClient() override = default;
  private:
  + bool timerScheduled_{false};
  std::string host_;
  uint16_t port_;
  std::shared_ptr<quic::QuicClientTransport> quicClient_;
  