Test docker login for container registry

.gitlab-ci.yml

+before_script:
+  - docker login -u $CI_REGISTRY_USER -p $CI_REGISTRY_PASSWORD $CI_REGISTRY
+
+
 image: ${CI_DEPENDENCY_PROXY_GROUP_IMAGE_PREFIX}/node:12.16.3
 
 # Info: http://docs.gitlab.com/ee/ci/docker/using_docker_images.html#what-is-a-service