Follow the new PTI for document build

For compliance with the Project Testing Interface as
described in [1]:
[1] https://governance.openstack.org/tc/reference/project-testing-interface.html
For more detials information, please refer to [2]:
[2] http://lists.openstack.org/pipermail/openstack-dev/2017-December/125710.html

Change-Id: I648a78396a2e27f1d7197e89cddba73f8aa858aa
3 files changed