ci: Always re-tag the "latest" container when run on master
This fixes the issue that containers first-created through an MR would not get tagged when merged to master because the container was already existing.
Due to an influx of spam, we have had to impose restrictions on new accounts. Please see this wiki page for instructions on how to get full permissions. Sorry for the inconvenience.
This fixes the issue that containers first-created through an MR would not get tagged when merged to master because the container was already existing.