This optimization never worked -- there were four usages of
the update_peer_info function and in all of them some of
the peer_info fields were set or should be set:
* sync_raft_topology_nodes/process_normal_node: e.g. tokens is set
* sync_raft_topology_nodes/process_transition_node: host_id is set
* handle_state_normal: tokens is set
* storage_service::on_change: get_peer_info_for_update could potentially
return a peer_info with all fields set to empty, but this shouldn't
be possible, host_id should always be set.
Moreover, there is a bug here: we extract host_id from the
states_ parameter, which represent the gossiper application
states that have been changed. This parameter contains host_id
only if a node changes its IP address, in all other cases host_id
is unset. This means we could end up with a record with empty
host_id, if it wasn't previously set by some other means.
We are going to fix this bug in the next commit.
e0072f7cb3