Add CLI reference for Sahara

According to https://github.com/openstack/governance/blob/master/reference/programs.yaml
Sahara is an integrated project since Juno. Clients of integrated projects
should be available in the CLI reference.

Change-Id: I7196b78e8b5753464a55ddd7ff34b3a413f20f6d
Merge "Add CLI reference for Sahara"