The new service, `auth_integration`, has taken over the responsibility
over managing effective service levels from `service_level_controller`.
However, before these changes, it still accessed `auth::service` via
the service level controller. Let's change that.
Note that we also remove a check that `auth::service` has been
initialized. It's not necessary anymore because the lifetime of
`auth_integration` is strictly nested within the lifetime of `auth::service`.
In actuality, `service_level_controller` should lose its reference to
`auth::service` completely. All of the management over effective service
levels has already been moved to `auth_integration`. However, the
referernce is still needed when dropping a distributed service level
because we need to update the corresponding attribute for relevant
roles.
That should not lead to invalid accesses, though. Dropping a service level
should not be possible when `auth::service` is not initialized.
(cherry picked from commit dd5a35dc67)
687956f9f4