testnode: disallow frontend access to all folders, avoiding publishing private repositories
The current status of testnode is quite dangerous. If we release a new version and we start using it, all private repositories are going to be publicly available through testnode frontends, like explained in https://nexedi.erp5.net/web_page_module/6035.
To avoid such issue, Julien and me would like to disable any access by default. Access would be enabled for now only when a "test-url" is given in test suite parameters. So this should not break the very few test suites using remote web browsers, and such test suites must use public repositories. We will see later how to do better, it is just a first step to avoid exposing all private code.