This is an alternative to Iccf24a72cf82592bae8c699f9f857aa54fc74f10
which removes the 404 scraping tool. It creates a zuul user and
enables login via the system-config per-project ssh key, and then runs
the 404 scraping script against it periodically.
Change-Id: I30467d791a7877b5469b173926216615eb57d035