Move cod_rabbitmq_agents_cloud from ohpc-ops.yaml to cod.yaml

- { name: 'cod_rabbitmq_agents_cloud', tags: 'cod_rabbitmq_agents_cloud', when: cod_deploy } should be moved from ohpc-ops.yaml to cod.yaml and probably we can remove the condition of cod_deploy, because cod.yaml is intended to always run on headnode.

Update the docs in cod-heat-stack project accordingly.