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

modules/openstack_project/files/jenkins_job_builder/config/manuals.yaml

@@ -137,6 +137,11 @@
     prebuilders:
       - gerrit-git-prep
 
+    properties:
+      - inject:
+          script-file: /usr/local/jenkins/slave_scripts/docbook-properties.sh
+          properties-file: gerrit-doc.properties
+
     maven:
       maven-name: Maven3
       root-module: