There seem to be compatibility issues with container updates within the
same tag. These updates happen every time we run Ansible and are usually
desired, as they can fix security issues (esp. in the base image).
However, if the update cannot be trusted to run without manual intervention,
we have to pin the version and check for updates manually.
Docker does not take the tzdata from host systems, so the
timezone needs to be set individually.
Otherwise dates without explicit timezone information or Z will
be generated or interpreted in the wrong timezone
(such as dokuwiki signatures)
