fix duplicate headers on non successful responses (#7403)

Signed-off-by: yaron2 <schneider.yaron@live.com>

pkg/api/http/directmessaging.go

@@ -254,13 +254,16 @@ func (a *api) onDirectMessage(w http.ResponseWriter, r *http.Request) {
 	// Log with debug level and send the error to the client in the body
 	log.Debugf("HTTP service invocation failed to complete with error: %v", err)
 
+	var headersSet bool
+
 	if resp != nil {
 		resp.Close()
 
 		// Set headers if present (if resp is not nil, they haven't been sent already)
 		headers := resp.Headers()
 		if len(headers) > 0 {
 			invokev1.InternalMetadataToHTTPHeader(r.Context(), headers, w.Header().Add)
+			headersSet = true
 		}
 	}
 
@@ -270,7 +273,7 @@ func (a *api) onDirectMessage(w http.ResponseWriter, r *http.Request) {
 	)
 	switch {
 	case errors.As(err, &codeErr):
-		if len(codeErr.headers) > 0 {
+		if len(codeErr.headers) > 0 && !headersSet {
 			invokev1.InternalMetadataToHTTPHeader(r.Context(), codeErr.headers, w.Header().Add)
 		}
 		respondWithHTTPRawResponse(w, &UniversalHTTPRawResponse{