Right now `ephemeral` is booting via a virtiofsd export of the source image.

However the default way we mount the image via `--mount=type=image` with podman doesn't mount the overlayfs with `nfs_export=on` which means `name_to_handle_at` doesn't work, which means we're subject to file descriptor exhaustion.

The best thing here is to change container-libs to support mounting with `nfs_export=on`.