There's such a reference on storage_service itself, it can use this->_sys_dist_ks instead thus making its API (both internal and external) a bit simpler.
Closesscylladb/scylladb#22483
* github.com:scylladb/scylladb:
storage_service: Drop sys_dist_ks argument from track_upgrade_progress_to_topology_coordinator()
storage_service: Drop sys_dist_ks argument from raft_state_monitor_fiber()
storage_service: Drop sys_dist_ks argument from join_topology()
storage_service: Drop sys_dist_ks argument from join_cluster()