Also:
- docker-compose: move the swh-indexer-journal-client in the journal "section"
- swh-scheduler: add SWH_CONFIG_FILENAME and SWH_SCHEDULER_CONFIG_FILE env vars
- in all the swh-scheduler related services. Also configure the CELERY_BROKER_URL env var.
These allow to use the swh-scheduler directly in the container without
any cmdline option, as well as the celery command.