Mount LXD container rootfs on the host machine

If you're using ZFS as your LXD storage backend (and you should be!) then it's really easy to make a container's rootfs available to the host for operations such as rsyncs. Make migrating LXC from one machine to another super easy :)

mkdir /mnt/mountpoint
zfs set mountpoint=/mnt/mountpoint yourpool/containers/yourvm
mount /mnt/mountpoint