[SAC] LXD containers deploy via ansible

I've added the first LXD container deploy support to the new
ansible-deployment repository. It was done for the osgeo7 nginx
container, to secure proxy device configurations.

I did run the deploy once and it correctly figured out there were
no changes to apply to the configuration, so seemed to work fine.

We could add the configuration for each and every container to the
playbook, to have a unified view of all configurations, but I did not
do that for now as I'm just trying to save the work done for a
specific ticket (https://trac.osgeo.org/osgeo/ticket/2521).

How do other SAC members feel about this ansible setup ?