private static boolean allChildrenCanBeDeprovisioned(Map<Optional<String>, List<Node>> nodesByParent, Node host) {
        return getChildren(nodesByParent, host).stream().allMatch(HostCapacityMaintainer::canDeprovision);
    }
Try to allocate the preprovision cluster capacity.

@param mutableNodes represents all nodes in the node repo.  As preprovision capacity is virtually allocated
                    they are added to {@code mutableNodes}
@return the part of a cluster capacity it was unable to allocate, if any
node-repository/src/main/java/com/yahoo/vespa/hosted/provision/maintenance/HostCapacityMaintainer.java