Added machine-id file to /etc in containers built off container UUID

The first 32 characters (16 hex-encoded bytes) of a container's UUID are placed
in a file in the container's context path, then bind mounted to /etc/machine-id
This provides each container with an ID unique from the host system

Fixed docker diff test case to include new file, preventing breakage

Docker-DCO-1.1-Signed-off-by: Matt Heon <mheon@redhat.com> (github: mheon)
Added support for journal forwarding to host.

On creating a new container on a systemd-booted system, Docker
will create a directory in its context root to hold journal logs
and symlink this into /var/log/journal/$CONTAINER_UUID on the host.
This is then bind-mounted in the container as
/var/log/journal/$CONTAINER_UUID