Added missing license headers

ansible/roles/dns/tasks/agent.yml

ansible/roles/dns/tasks/main.yml

ansible/roles/dns/tasks/server.yml

ansible/roles/docker-container/tasks/certs/ca_cert.yml

ansible/roles/docker-container/tasks/certs/cert.yml

ansible/roles/docker-container/tasks/configs/copy_config.yml

...ble/roles/docker-container/tasks/configs/copy_configs.yml

ansible/roles/docker-container/tasks/configs/secret.yml

ansible/roles/docker-container/tasks/configs/secrets.yml

ansible/roles/docker-container/tasks/docker.yml

ansible/roles/docker-container/tasks/facts/common.yml

ansible/roles/docker-container/tasks/facts/container.yml

ansible/roles/docker-container/tasks/main.yml

ansible/roles/docker-container/tasks/service.yml

ansible/roles/docker-container/tasks/swarm.yml

ansible/roles/docker-engine/tasks/centos.yml

ansible/roles/docker-engine/tasks/main.yml

ansible/roles/docker-engine/tasks/ubuntu.yml

ansible/roles/nfs/tasks/main.yml

ansible/roles/prepare-certs/tasks/main.yml