Allow Docker to use insecure registry when deployed by Kayobe

Kolla Ansible has recently updated the default Docker configuration to
stop using an insecure registry [1]. To avoid breaking existing Kayobe
deployments, automatically set docker_registry_insecure to true if we
deploy a registry without TLS.

[1] https://review.opendev.org/c/openstack/kolla-ansible/+/805449

Change-Id: Ifec7102812b5503cb02f207098192e99e7193d49