Add a simple job to test dind

.gitlab-ci.yml

+quick_dind_test:
+  image: docker:git
+  services:
+    - name: docker:dind
+      alias: docker
+  script:
+    - docker image ls
+  tags:
+    - docker
+
 shellcheck:
   image: tecnalia-docker-dev.artifact.tecnalia.com/koalaman/shellcheck-alpine
   script: shellcheck scripts/*sh