Add publications index job.

Change-Id: Icd841aa28f819df15d389abcdc5cb37ff33d4354
Reviewed-on: https://review.openstack.org/33563
Reviewed-by: Jeremy Stanley <fungi@yuggoth.org>
Reviewed-by: Monty Taylor <mordred@inaugust.com>
Approved: Jeremy Stanley <fungi@yuggoth.org>
Tested-by: Jenkins