This patch adds the service user rotation feature, which provides two
actions:
- list-service-usernames
- rotate-service-user-password
The first lists the possible usernames that can be rotated. The
second action rotates the service, and is tested via the func-test-pr.
Change-Id: Ia94ab3d54cd8a59e9ba5005b88d3ec1ff87019b1
func-test-pr: https://github.com/openstack-charmers/zaza-openstack-tests/pull/1029