promoter: Use force parameter when removing images

http://docs.ansible.com/ansible/latest/modules/docker_image_module.html

The current promoter does not actually untag and delete the
images from the promoter's local disk, yielding eventual
out of space issues for /var/lib/docker.

This adds the force option, which when used together with
state: absent should actually remove the bits.

(from doc: state)

"When absent an image will be removed. Use the force option to
un-tag and remove all images matching the provided name."

(from doc: force)

"Use with state absent to un-tag and remove all images matching the
specified name. Use with state present to build, load or pull an
image when the image already exists."

Change-Id: Ie0d801d167986696f72207d4ece571529c50daa2

ci-scripts/container-push/container-push.yml

@@ -159,6 +159,7 @@
             name: "trunk.registry.rdoproject.org/{{ rdoproject_namespace }}/centos-binary-{{ item[0] }}"
             tag: "{{ item[1] }}"
             state: absent
+            force: yes
           with_nested:
             - "{{ built_images.stdout_lines }}"
             - ["{{ full_hash }}", "{{ named_label }}"]
@@ -172,6 +173,7 @@
             name: "docker.io/{{ dockerhub_namespace }}/centos-binary-{{ item[0] }}"
             tag: "{{ item[1] }}"
             state: absent
+            force: yes
           with_nested:
             - "{{ built_images.stdout_lines }}"
             - ["{{ full_hash }}", "{{ named_label }}"]