@Override
    public int hashCode() {
        return node.hashCode();
    }
When a node goes from an up state to a down state, update this flag with the start timestamp the node had before going down.
The cluster state broadcaster will use this to identify whether distributors have restarted.
clustercontroller-core/src/main/java/com/yahoo/vespa/clustercontroller/core/NodeInfo.java