Now that there is no more race between the containers for
preparing the volume, we can use it for podman as well...

Previously we risked ending up with not copying the contents
of /var from the container image, which made it not work.

The volume is created as empty, so make sure that we run a
container to do the initial copy of /var from the image.

This is to avoid race conditions later on, where the preload
starts to use the created volume for packing up the tarball.

The messages are different between "inspect" and "container inspect",
and also changed a bit in format between Podman v1 and Podman v2.

Support all of them, for compatibility with different versions of
Docker and Podman. Was causing restarts and failures, with KIC.

Since FailFastError was just another `error`, all errors were technically `FailFastErrors`.

This code makes `FailFastError` a struct which implements the error interface, so that now errors can be distinctly identified as `FailFastError`'

Also added a unit test to prove that this works now.