fix: de-duplicate backend servers list mapped from topology

harmony/src/modules/okd/bootstrap_load_balancer.rs

@@ -54,6 +54,7 @@ impl OKDBootstrapLoadBalancerScore {
             },
         }
     }
+
     fn topology_to_backend_server(topology: &HAClusterTopology, port: u16) -> Vec<BackendServer> {
         let mut backend: Vec<_> = topology
             .control_plane