Publish cliff and stevedore docs on openstack.org

The cliff and stevedore docs previously lived on readthedocs.org, but
the builds there are not working because our doc build depends on some
things we cannot configure to run there (we don't get to inject our own
conf.py).

This commit turns on the publishing jobs for those libraries for
docs.openstack.org. We will turn off the rtfd.org jobs after we have the
new copies publishing and we update the references in the package
metadata that point to the documentation.

Change-Id: I1c9f788f61675c6720292cff00245d7f1a0c4977
Closes-Bug: #1374073
Merge "Publish cliff and stevedore docs on openstack.org"