Support deploy tokens in Auto DevOps template

Auto DevOps template should recognize if we have a deploy token (https://gitlab.com/gitlab-org/gitlab-ce/issues/31591) exposed as an environment variable (https://gitlab.com/gitlab-org/gitlab-ce/issues/44447), and use it to create cluster secrets instead of the temporary token.

This affects only private/internal projects, for public projects we don't need to create the secret.

Check if CI_DEPLOY_USER and CI_DEPLOY_PASSWORD are defined, and use them when creating secrets on Kubernetes in the Auto DevOps template.

Edited Apr 24, 2018 by Mayra Cabrera