fix bug 981581: Bugfix for "new" link annotation on absolute URLs

Turns out the link annotation algorithm was sensitive to a site base url with or without trailing slash. That made [pages like this](https://developer.mozilla.org/en-US/docs/MDN/Doc_status/Editorial_reviews) show links as pages in need of creation, when in fact the pages did exist. 

This PR tweaks the test to reflect prod more accurately & trigger the bug, and makes the algo more robust.