Publish to its registry

The docker images are pushed to its-registry

• Add a new stage: publish
• Add a new job: Push to Container Registry as part of the publish stage
• Disables the job Scan with Tenable:
• The containers will be tagged as its-registry.unl.edu/unl-its/docker-ci/NAME_OF_THE_CONTAINER

TODO: Update the list of all projects affected (issue #2 (closed) )