Changes publishing API test helpers

Changes the publishing API test helpers to deal with situations where
we don't care about the response body

In support of https://www.pivotaltracker.com/story/show/79180560
(Part of a larger piece of work detailed here: https://gov-uk.atlassian.net/wiki/x/XIDf)
This line does nothing as it stands...  It's also a duplicate of line 14.