set publish branch location for cinder admin docs

Before it was just putting files into /local, this will publish things
to the correct location.

Change-Id: I0b08dc97294c55a2c83f754d94528429e6090f92
Reviewed-on: https://review.openstack.org/26123
Reviewed-by: James E. Blair <corvus@inaugust.com>
Reviewed-by: John Griffith <john.griffith@solidfire.com>
Approved: Jeremy Stanley <fungi@yuggoth.org>
Reviewed-by: Jeremy Stanley <fungi@yuggoth.org>
Tested-by: Jenkins