Kafka container doesn't have a volume mapping for persisting data

There is no volume mapping for persisting Kafka data. Although unlikely, it can cause data loss.

If there's no reason not to use the volume mapping, can I add it?

```yaml
docker_container:
name: kafka{{ groups['kafkas'].index(inventory_hostname) }}
image: "{{ kafka_image }}"
state: started
recreate: true
restart_policy: "{{ docker.restart.policy }}"
env: "{{ kafka_env_vars }}"
ports: "{{ ports_to_expose }}"
volumes:
- "{{ config_root_dir }}/kafka/certs:/config"
pull: true
```