In change I322a40404d8287748fe8c3a8d6dc1256d935d84a we switched from an
'auth_credential_required' field in the response to an 'auth_credential'
object. Correct the api-ref.
While we're alphabetize the response parameters.
Change-Id: Ie5dd375c4922cee895e4dfe25defb70a0b5e21a7
Signed-off-by: Stephen Finucane <sfinucan@redhat.com>