Fix issue when there are 2 similar Routes from different SubRouters

[EvilLord666]

This PR reproduces the issue - #17 (test)

func TestHandleFuncForSubRouterSameName(t *testing.T) {
	internalSubNet := "192.168.30.0"
	handler := NewWebApiHandler(true, internalSubNet)
	objectResource := "/api/object/"
	handler.HandleFunc(handler.Router, objectResource, func(writer http.ResponseWriter, request *http.Request) {
	}, "GET")
	service1Router := handler.Router.PathPrefix("/service1").Subrouter()
	handler.HandleFunc(service1Router, objectResource, func(writer http.ResponseWriter, request *http.Request) {
	}, "POST")
	checkOptionRouteCors(t, handler.Router, "/api/object/", internalSubNet, "*", "OPTIONS,GET")
	checkOptionRouteCors(t, handler.Router, "/service1/api/object/", internalSubNet, "*", "OPTIONS,POST")
}

[EvilLord666]

done in 1.4.1