docs(openstack): instructions did not work.

The openstack instructions were a mix of new/old commands and
wouldn't work on a lot of openstack installs.

These documentation and changes to the provisioning script should
allow for more variation in openstack installs.

This has been tested as working against both a Havana and Juno release
of Openstack.
true. If this documentation is around [devstack](http://docs.openstack.org/developer/devstack/) or something more vanilla then we should use that approach and call out provider-specific documentation inline or elsewhere. looks fine as-is