private Result canSetStateUp(NodeInfo nodeInfo, NodeState oldWantedState) {
        if (oldWantedState.getState() == UP)
            return alreadySet(); // The description is not significant when wanting to set the state to UP

        State reportedState = nodeInfo.getReportedState().getState();
        if (reportedState != UP)
            return disallow("Refuse to set wanted state to UP, since the reported state is not UP (" + reportedState + ")");

        return allow();
    }
Checks if a node can be upgraded.

@author Haakon Dybdahl
clustercontroller-core/src/main/java/com/yahoo/vespa/clustercontroller/core/NodeStateChangeChecker.java