leftover block device in `/ostree/bootc/storage/` after bootc install

[jbtrystram]

After building a CoreOS disk image with bootc install to filesystem there is a leftover block device under :

root@cosa-devsh:~# ls /ostree/bootc/storage/overlay/backingFsBlockDev -l
brw-------. 1 root root 259, 3 Apr  8 08:28 /ostree/bootc/storage/overlay/backingFsBlockDev

I think this is a leftover because none of blkid,lsblk,lsof yield anything useful.

[cgwalters]

This is actually created by containers-storage (podman/skopeo via https://github.com/containers/container-libs/)

It'd need some investigation, we may be able to entirely delete it, or we could initialize it on firstboot.