private double skewWith(NodeResources resources) {
        if (parent.isEmpty()) return 0;
        NodeResources free = freeParentCapacity.justNumbers().subtract(resources.justNumbers());
        return Node.skew(parent.get().flavor().resources(), free);
    }
Returns the host priority, based on allocation skew, of this compared to other
node-repository/src/main/java/com/yahoo/vespa/hosted/provision/provisioning/NodeCandidate.java