For services that currently read that environment variable (swh-vault
[1]), this will specify explicitely the configuration file to use.
For others, that won't change a think as they need adaptations to do
so (swh-storage, swh-objstorage, swh-scheduler).
[1] https://forge.softwareheritage.org/source/swh-vault/browse/master/swh/vault/api/server.py$230
Related T1533