[rdf] Failing tests in caused by localFetch

[tpluscode]

Test cases which intend to test a failure when file is not found fail with Error: done() called multiple times in test. This started happening since file-fetch update. I don't think it should cause any issues but we might need to revisit...

re https://github.com/zazuko/barnard59/pull/231#pullrequestreview-1762266148