void setAllBucketsToState(BucketState state) {
        for (Map.Entry<BucketKeyWrapper, ProgressToken.BucketEntry> entry
                : buckets.entrySet()) {
            entry.getValue().setState(state);
        }
    }
@param bucket BucketId to be split into two buckets. Bucket's used-bits
do not need to match the ProgressToken's current distribution bit count,
as it is assumed the client knows what it's doing and will bring the
token into a consistent state eventually.
documentapi/src/main/java/com/yahoo/documentapi/ProgressToken.java