coverity: fix TOCTOU problem when creating chroot

coverity: fix TOCTOU problem when creating chroot

It is believed that checking for existence of a directory or a file
before an action is useless since it could be created after the check
and before the action. Therefore, it is better to just try to do the
action and handle any failure gracefully.

When setting up the chroot, instead of checking if it already exists, we
create it and don't display an error if it is already set up.