private static int getNumBuckets(int numBucketBits) {
        return 1 << numBucketBits;
    }
Returns the number of buckets that the given number of bucket bits will allow.

@param numBucketBits The number of bits to use for bucket id.
@return The number of buckets allowed.
vdslib/src/main/java/com/yahoo/vdslib/BucketDistribution.java