conf/debian-jessie: Use consistent /proc, /sys and /sys/fs/cgroup (v2)
conf/debian-jessie: Use consistent /proc, /sys and /sys/fs/cgroup (v2)

Without this a systemd container won't start:
> $ lxc-start -n vagrant-base-stretch-amd64
> Failed to mount cgroup at /sys/fs/cgroup/systemd: Permission denied
> [!!!!!!] Failed to mount API filesystems, freezing.
> Freezing execution.

See upstream commit: lxc-1.1.0.rc3-12-gf24a52d [Use consistent /proc, /sys and /sys/fs/cgroup (v2)]

sephii/vagrant-lxc-base-boxes,obnoxxx/vagrant-lxc-base-boxes,DavBfr/vagrant-lxc-base-boxes,DavBfr/vagrant-lxc-base-boxes