should clear HttpContext's filters when reset

[dk-lockdown]

see manager.go

// ServeHTTP http request entrance.
func (s *DefaultHttpWorker) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	hc := s.pool.Get().(*h.HttpContext)
	defer s.pool.Put(hc)

	hc.Request = r
	hc.ResetWritermen(w)
	hc.Reset()

	// now only one filter http_connection_manager, so just get it and call
	err := s.ls.nf.OnData(hc)

	if err != nil {
		s.pool.Put(hc)
		logger.Errorf("ServeHTTP %s", err)
	}
}

func (hcm *HttpConnectionManager) OnData(hc *pch.HttpContext) error {
	hc.Ctx = context.Background()
	err := hcm.findRoute(hc)
	if err != nil {
		return err
	}
	hcm.addFilter(hc)
	hcm.handleHTTPRequest(hc)
	return nil
}

What happened:

What you expected to happen:

How to reproduce it (as minimally and precisely as possible):

Anything else we need to know?: