document Jenkins user permissions

This document the required permissions of the Zuul Jenkins user.

Change-Id: Id977e3813f943b032c7628d8cdc663b3bdbb688d
Reviewed-on: https://review.openstack.org/16528
Reviewed-by: Jeremy Stanley <fungi@yuggoth.org>
Approved: Clark Boylan <clark.boylan@gmail.com>
Reviewed-by: Clark Boylan <clark.boylan@gmail.com>
Tested-by: Jenkins
1 file changed