remove some http hard code (#2047)

Co-authored-by: yonbiaoxiao <yonbiaoxiao@tencent.com>

api/handler/http/http.go

@@ -28,7 +28,7 @@ type httpHandler struct {
 func (h *httpHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 	service, err := h.getService(r)
 	if err != nil {
-		w.WriteHeader(500)
+		w.WriteHeader(http.StatusInternalServerError)
 		return
 	}
 
@@ -39,7 +39,7 @@ func (h *httpHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 
 	rp, err := url.Parse(service)
 	if err != nil {
-		w.WriteHeader(500)
+		w.WriteHeader(http.StatusInternalServerError)
 		return
 	}