install-docker: add option to use buildset registry

At the moment, the build registry is not used inside Kubernetes jobs
and it is required to override the entire pre.yaml just to enable it.

This patch adds an option of using docker_use_buildset_registry inside
install-docker which can be used in order to install Docker and letting
it use the buildset registry simply by adjusting the job.vars

Change-Id: I1b42eac6accbf7c350aee76d18a823ba6327548d

roles/install-docker/README.rst

@@ -18,6 +18,13 @@ An ansible role to install docker and configure it to use mirrors if available.
    By default this role adds repositories to install docker from upstream
    docker. Set this to False to use the docker that comes with the distro.
 
+.. zuul:rolevar:: docker_use_buildset_registry
+   :default: False
+
+   This role does not enable the usage of the buildset registry by default,
+   this variable allows enabling the usage of the buildset registry after
+   installing Docker.
+
 .. zuul:rolevar:: docker_compose_install
    :default: False
 

roles/install-docker/defaults/main.yaml

@@ -1,5 +1,6 @@
 use_upstream_docker: True
 docker_group: docker
+docker_use_buildset_registry: false
 # NOTE(cloudnull): Packages are loaded through distro specific variables.
 #                  The default option will return an empty list which
 #                  allows folks to override these lists as they see fit.

roles/install-docker/tasks/main.yaml

@@ -80,3 +80,11 @@
 - name: Dump installed docker details
   debug:
     msg: '{{ docker_installed_version }}'
+
+- name: Use buildset registry
+  include_role:
+    name: use-buildset-registry
+  vars:
+    buildset_registry_docker_user: root
+  when:
+    - docker_use_buildset_registry | bool

test-playbooks/registry/buildset-registry-k8s-docker.yaml

@@ -2,8 +2,7 @@
   roles:
     - role: clear-firewall
     - role: install-kubernetes
-    - role: use-buildset-registry
-      buildset_registry_docker_user: root
+      docker_use_buildset_registry: true
   tasks:
     - name: Wait for cluster to come up
       command: kubectl cluster-info