An oddity (bug?) means that we don't preserve empty cgroups in in the criu
cgset, since we don't dump it. So we do need to move things into tasks.

(This probably got commented out due to a bug in the Ubuntu kernel that I
ran across [1] which should be fixed shortly :)

[1]: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1588056Signed-off-by: Tycho Andersen <tycho.andersen@canonical.com>
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>