public List<Node> performOn(NodeList nodes, BiFunction<Node, Mutex, Node> action) {
        return performOn(nodes, __ -> true, action);
    }
Performs an operation requiring locking on all given nodes.

@param action the action to perform
@return the set of nodes on which the action was performed, as they became as a result of the operation
node-repository/src/main/java/com/yahoo/vespa/hosted/provision/node/Nodes.java