Reinstate docker tag cleanup

This uses a new method of calculating the cutoff time which does not
require executing code on the executor.

Change-Id: I92e71727e24281a31cb7caf0b78dd17a5aaae129
Co-Authored-By: Clark Boylan <clark.boylan@gmail.com>

roles/promote-docker-image/tasks/promote-cleanup.yaml

@@ -3,18 +3,18 @@
     url: "https://hub.docker.com/v2/repositories/{{ zj_image.repository }}/tags?page_size=1000"
     status_code: 200
   register: tags
-# - name: Set cutoff timestamp to 24 hours ago
-#   command: "python3 -c \"import datetime; print((datetime.datetime.utcnow()-datetime.timedelta(days=1)).strftime('%Y-%m-%dT%H:%M:%fZ'))\""
-#   register: cutoff
-# - name: Delete all change tags older than the cutoff
-#   no_log: true
-#   loop: "{{ tags.json.results }}"
-#   loop_control:
-#     loop_var: zj_docker_tag
-#   when: zj_docker_tag.last_updated < cutoff.stdout and zj_docker_tag.name.startswith('change_')
-#   uri:
-#     url: "https://hub.docker.com/v2/repositories/{{ zj_image.repository }}/tags/{{ zj_docker_tag.name }}/"
-#     method: DELETE
-#     status_code: [200, 204]
-#     headers:
-#       Authorization: "JWT {{ jwt_token.json.token }}"
+- name: Delete all change tags older than the cutoff
+  no_log: true
+  loop: "{{ tags.json.results }}"
+  loop_control:
+    loop_var: zj_docker_tag
+  when:
+    - zj_docker_tag.name.startswith('change_')
+    # Was updated > 24 hours ago:
+    - "{{ ((ansible_date_time.iso8601 | regex_replace('^(....-..-..)T(..:..:..).*Z', '\\1 \\2') | to_datetime) - (zj_docker_tag.last_updated | regex_replace('^(....-..-..)T(..:..:..).*Z', '\\1 \\2') | to_datetime)).seconds > 86400 }}"
+  uri:
+    url: "https://hub.docker.com/v2/repositories/{{ zj_image.repository }}/tags/{{ zj_docker_tag.name }}/"
+    method: DELETE
+    status_code: [200, 204]
+    headers:
+      Authorization: "JWT {{ jwt_token.json.token }}"