During cell_v2 update external_deploy_steps_tasks.yaml is empty

[Piotr Kopec]

Description
===========

During update procedure described in [1] when trying to do minor update of cell stack the external_deploy_steps_tasks.yaml playbook downloaded to /var/lib/mistral is empty because of missing `OS::TripleO::Services::ContainerImagePrepare` service in CellController role.

Steps to reproduce
==================
- Deploy cellv2
- Follow update procedure
- after openstack overcloud external-update run --tags container_image_prepare --stack cell1 check content of external_deploy_steps_tasks.yaml
- file is empty list

Expected result
===============
File contains update playbook.

[1]: https://docs.openstack.org/tripleo-docs/latest/upgrade/minor_update.html

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.opendev.org/675795

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.opendev.org/675795
Committed: https://git.openstack.org/cgit/openstack/tripleo-heat-templates/commit/?id=2b2216bf6773ebd3a0d7dfead1f766146c654dc3
Submitter: Zuul
Branch: master

commit 2b2216bf6773ebd3a0d7dfead1f766146c654dc3
Author: Piotr Kopec <email address hidden>
Date: Mon Aug 12 00:27:17 2019 +0200

    Add ContainerImagePrepare service to CellController role

    The CellController role does not have ContainerImagePrepare
    service. This result in empty external_deploy_steps_tasks.yaml
    and does not update container images when trying to update
    the cell stack.

    Change-Id: Ib12d99be11e34b77fe3697c9ce09f84e4a1294f3
    Closes-Bug: 1839789

[OpenStack Infra (hudson-openstack)]

This issue was fixed in the openstack/tripleo-heat-templates 11.2.0 release.