public NodeState getNodeState(Node node) {
        return getNodes(node.getType()).getNodeState(node.getIndex());
    }
Returns the state of a node.
If the node is not known this returns a node in the state UP (never null) if it has lower index than the max
and DOWN otherwise.
vdslib/src/main/java/com/yahoo/vdslib/state/ClusterState.java