podman: Do not purge volumes when a pull fails
Whenever podman fails to run a container 3 times in a row, we system purge
to hopefully fix any potential issue in our layer DB, but it also ends up removing all the volumes. Volumes may be used to cache tens of gigabytes of data, so re-downloading them can be quite expensive.
Let's not remove the volumes, and instead just purge all the containers and container images.