Use gitlab automated docker build

.gitlab-ci.yml

@@ -10,27 +10,8 @@
 #
 # Job definition for automated Docker image building
 #
-create_image:
-    stage: build
-
-    #
-    # Select proper runner node
-    #
-    tags:
-        - docker-image-build
-
-    #
-    # This section is unused, but required by Gitlab-CI
-    #
-    script:
-        - echo 'Create Docker image'
-
-    #
-    # Set parameters for image building
-    #
-    variables:
-        TO: 'docker.cern.ch/security-services/code-checking:latest'
-        DOCKER_INFO: 'true' # Display Docker informations
-        DOCKER_LOGIN_SERVER: 'docker.cern.ch'
-        DOCKER_LOGIN_USERNAME: $_DOCKER_USERNAME
-        DOCKER_LOGIN_PASSWORD: $_DOCKER_PASSWORD
+build:
+  stage: build
+  tags:
+    - docker-image-build
+  script: "" # unused but this line is required by GitLab CI