production-playbook logs : don't use ansible_date_time

ansible_date_time is actually the cached fact time that has little
bearing on the actual time this is running [1] -- which is what you
want to see when, for example, tracing backwards to see why some runs
are randomly timing out.

[1] https://docs.ansible.com/ansible/latest/user_guide/playbooks_vars_facts.html#ansible-facts

Change-Id: I8b5559178e29f8604edf6a42507322fc928afb21

playbooks/zuul/run-production-playbook.yaml

@@ -16,9 +16,13 @@
     - name: Run the production playbook and capture logs
       block:
 
+      - name: Get a current timestamp
+        set_fact:
+          _log_timestamp: "{{ lookup('pipe', 'date +%Y-%m-%dT%H:%M:%S') }}"
+
       - name: Log a playbook start header
         become: yes
-        shell: 'echo "Running {{ ansible_date_time.iso8601 }}: ansible-playbook -v -f {{ infra_prod_ansible_forks }} /home/zuul/src/opendev.org/opendev/system-config/playbooks/{{ playbook_name }}" > /var/log/ansible/{{ playbook_name }}.log'
+        shell: 'echo "Running {{ _log_timestamp }}: ansible-playbook -v -f {{ infra_prod_ansible_forks }} /home/zuul/src/opendev.org/opendev/system-config/playbooks/{{ playbook_name }}" > /var/log/ansible/{{ playbook_name }}.log'
 
       - name: Run specified playbook on bridge.o.o and redirect output
         become: yes
@@ -113,7 +117,7 @@
           copy:
             remote_src: yes
             src: "/var/log/ansible/{{ playbook_name }}.log"
-            dest: "/var/log/ansible/{{ playbook_name }}.log.{{ ansible_date_time.iso8601 }}"
+            dest: "/var/log/ansible/{{ playbook_name }}.log.{{ _log_timestamp }}"
 
         - name: Cleanup old playbook logs on bridge
           when: not infra_prod_playbook_collect_log