Pass root to chroot to for chroot Untar

Pass root to chroot to for chroot Untar

This is useful for preventing CVE-2018-15664 where a malicious container
process can take advantage of a race on symlink resolution/sanitization.

Before this change chrootarchive would chroot to the destination
directory which is attacker controlled. With this patch we always chroot
to the container's root which is not attacker controlled.

Signed-off-by: Brian Goff <cpuguy83@gmail.com>
Origin: upstream, https://github.com/moby/moby/pull/39292

Gbp-Pq: Name cve-2018-15664-01-pass-root-to-chroot-to-for-chroot-untar.patch