ironic role does not register keystone user multi region

When deploying a multi region deployment of Kolla Ansible you may set `enable_ironic` to true and `enable_keystone` to false.

This causes the `when` statement which calls register.yml within `roles/ironic/tasks/deploy.yml` to evaluate as false and the register tasks to be skipped.

This means that when Ironic is deployed using this combination the Ironic Keystone user is not created, and therefore Ironic does not work and will throw authentication errors in its log files.

One resolution to fixing this is to remove the `when: enable_keystone` condition from this task, but this would then break the stand alone Ironic deployment which uses noauth so is not acceptable.