In case a container image is corrupted `docker inspect` might fail:
# docker inspect --format='{{.Id}}' "${SUPERVISOR_IMAGE}"
Error response from daemon: readlink /mnt/data/docker/overlay2: invalid argument
In that same state the `docker images` command still shows the images.
Since `docker inspect` returns an error SUPERVISOR_IMAGE_ID will be empty
and a simple `docker pull` will be attempted. That does not suffice to
recover from a corrupted container image.
Use `docker images` to get the image ids and make sure to delete all
image ids found by that command.
Also don't use RuntimeDirectory since it deletes the runtime directory
between the service start attempts which defeats the purpose.
4f28a284be