private boolean closeBloomFilter(BloomFilterWriter bfw) throws IOException {
      boolean haveBloom = (bfw != null && bfw.getKeyCount() > 0);
      if (haveBloom) {
        bfw.compactBloom();
      }
      return haveBloom;
    }
For unit testing only.
@return the Bloom filter used by this writer.
hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/StoreFileWriter.java