private boolean anotherNodeInGroupAlreadyAllowed(Group group, Node node, String newDescription) {
        return group.getNodes().stream()
                .filter(configuredNode -> configuredNode.index() != node.getIndex())
                .map(configuredNode -> clusterInfo.getStorageNodeInfo(configuredNode.index()))
                .filter(Objects::nonNull)  // needed for tests only
                .map(NodeInfo::getUserWantedState)
                .anyMatch(userWantedState -> userWantedState.getState() == State.MAINTENANCE &&
                          Objects.equals(userWantedState.getDescription(), newDescription));
    }
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