Make a HTTP Post request to the server 'control' endpoint.

def MakeRequest(self, data):
    """Make a HTTP Post request to the server 'control' endpoint."""
    stats_collector_instance.Get().IncrementCounter("grr_client_sent_bytes",
                                                    len(data))

    # Verify the response is as it should be from the control endpoint.
    response = self.http_manager.OpenServerEndpoint(
        path="control?api=%s" % config.CONFIG["Network.api"],
        verify_cb=self.VerifyServerControlResponse,
        data=data,
        headers={"Content-Type": "binary/octet-stream"})

    if response.code == 406:
      self.InitiateEnrolment()
      return response

    if response.code == 200:
      stats_collector_instance.Get().IncrementCounter(
          "grr_client_received_bytes", len(response.data))
      return response

    # An unspecified error occured.
    return response