private static boolean groupContainsNode(Group group, Node node) {
        for (ConfiguredNode configuredNode : group.getNodes()) {
            if (configuredNode.index() == node.getIndex())
                return true;
        }

        return false;
    }
Returns a disallow-result, if there is a node in the group with wanted state != UP.
clustercontroller-core/src/main/java/com/yahoo/vespa/clustercontroller/core/NodeStateChangeChecker.java