Method unthrottle

include/proxy/http/HttpTunnel.h:761–767

}

inline void
HttpTunnelProducer::unthrottle()
{
  if (this->is_throttled()) {
    this->set_throttle_src(nullptr);
  }
}

inline HttpTunnel::FlowControl::FlowControl() : high_water(DEFAULT_WATER_MARK), low_water(DEFAULT_WATER_MARK) {}