Set container_uuid environment

If you are running with systemd as init 1 and specify the container_uuid environment
variable, systemd will create /etc/machine-id with the correct data.

Then on the host you can setup journald to watch the container.

systemd only allows 32 chars in the UUID stored in /etc/machine-id

Then we can later apply a different patch to setup journald to watch
containers from the host and log all syslog/stdout/stderr data together
int the hosts journal.

The following link explains what systemd expects to be setup.

http://www.freedesktop.org/wiki/Software/systemd/ContainerInterface/

This should replace

https://github.com/docker/docker/issues/3506

Docker-DCO-1.1-Signed-off-by: Dan Walsh <dwalsh@redhat.com> (github: rhatdan)
No the translation of the container_uuid to be a standard format as defined in wikipedia is new, and this is the format that systemd will understand for configuring the /etc/machine-id.  The end goal of this is to allow a system with systemd running on the host with journald and systemd running in a container with journald to communicate together.

We plan on moving Fedora and RHEL base images to include systemd by default and hope to allow users to optionally setup systemd based images, with all the pluggin working by default.

Then a developer could enable a systemd unit file in a Dockerfile with a simple script like this

FROM rhel7
RUN yum install httpd; systemctl enabled httpd.service
CMD /usr/bin/init

This would mean that the service would use the unit file as defined by the distribution rather then something thrown together by the developer.   It would be a nice alternative, and if we get this patch along with a follow-up to connect the journald to the container, All stdout/stderr and syslog messages from the container will show up in the journald of the host system.