Move to dynamic builders for SLES

This relies on: dev.gitlab.org:5005/cookbooks/gitlab-omnibus-builder/suse/sles12sp2

The FROM image is made from the SMT server itself with docker save, loaded locally with docker load, tagged as above, and then pushed.

We have private repository information for the SMT server, so all packages MUST be installed between zypper addrepo and zypper removerepo calls, WITHIN THE SAME LAYER

This is currently using the Open Build Service (OBS) build of NodeJS 6 (6.10.3), and not directly from a download form NodeJS .org

Relates to omnibus-gitlab#2254 (closed) Relates to https://gitlab.com/gitlab-org/gitlab-omnibus-builder/issues/9