Preload Docker images used by the Guacamole Docker composition

🗣 Description

This pull request preloads the Docker images used by the Guacamole Docker composition.

💭 Motivation and context

cisagov/cool-assessment-terraform currently has a NAT gateway in the operations subnet. This NAT gateway is only used when the Guacamole instance pulls the Docker images used by the Guacamole Docker composition at first start up. By preloading these Docker images in the Guacamole AMI, we remove the need for this NAT gateway resource.

See cisagov/cool-system#158 for more details.

🧪 Testing

All pre-commit hooks and molecule tests pass.

✅ Checklist

[x] This PR has an informative and human-readable title.
[x] Changes are limited to a single goal - eschew scope creep!
[x] All relevant type-of-change labels have been added.
[x] I have read the CONTRIBUTING document.
[x] These code changes follow cisagov code standards.
[x] Tests have been added and/or modified to cover the changes in this PR.
[x] All new and existing tests pass.

cisagov / ansible-role-guacamole