@Override
    public String toString() {
        return "LoadBalancer{" +
               "id=" + id +
               ", idSeed='" + idSeed + '\'' +
               ", instance=" + instance +
               ", state=" + state +
               ", changedAt=" + changedAt +
               '}';
    }
Returns a copy of this with instance set to given instance
node-repository/src/main/java/com/yahoo/vespa/hosted/provision/lb/LoadBalancer.java