CI: don't use insecure docker registries anymore

We are not using an plain http registry on the LAN anymore. We want to
only use https now.

.gitlab-ci-files/common-prepare.yml

@@ -8,23 +8,11 @@
   - 'which rsync || ( sudo apt-get update -y && sudo apt-get install rsync -y )'
   - 'which make || ( sudo apt-get update -y && sudo apt-get install make -y )'
 
-.enable_insecure_docker_registries: &enable_insecure_docker_registries
-  # Enable "insecure" docker registries
-  - |
-      cat <<EOD > /tmp/docker-daemon.json
-      {
-                "insecure-registries" : ["${DOCKER_REGISTRY_HOST}"]
-      }
-      EOD
-  - sudo cp /tmp/docker-daemon.json /etc/docker/daemon.json
-  - sudo systemctl restart docker.service
-
 .standard_job:
   tags: [kvm]
   before_script:
     - *ensure_docker
     - *ensure_rsync
-    - *enable_insecure_docker_registries
 
 .make_in_docker:
   extends: .standard_job