Fix bug with published related policies.

Mapping to #latest_edition then filtering by
published will get you false negatives if the
policy has a newer unpublished edition.
Merge pull request #1059 from alphagov/policy-weirdness

Fix bug with published related policies.



https://www.pivotaltracker.com/story/show/60688864

Mapping to #latest_edition then filtering by published will get you false negatives if the policy has a newer unpublished edition.

This is exacerbated by the unnatural conversion to editions when really the editions are linked to documents. See the tech debt around the edition/document conflux.