run-production-playbook-post: become when updating file time

This needs to be root to update the timestamp on the file to when the
job started.

Change-Id: Id313a83824fa43467a0eaab2dabffd9ee1bf10f5

playbooks/zuul/run-production-playbook-post.yaml

@@ -111,6 +111,7 @@
         modification_time_format: '%Y-%m-%dT%H:%M:%S'
         access_time: '{{ _log_timestamp }}'
         access_time_format: '%Y-%m-%dT%H:%M:%S'
+      become: yes
 
     - name: Cleanup old playbook logs on bridge
       when: not infra_prod_playbook_collect_log