In the create_job() RPC call, there's a parameter called `atomic_group_name`.

Looking through the master database, there are no valid atomic_group
entries.  AFAICT, the feature is unused in our installation, and I don't
know of any useful purpose we might put it to.

There's a fair amount of code (some of it kind of complicated) in the
scheduler for dealing with this unused feature.  It's likely we'd be
better off deleting it.