@Override
      public Boolean call() throws Exception {
        Compressor c = queue.take();
        CodecPool.returnCompressor(c);
        return c != null;
      }
Along with CodecPool, this is copied from the class of the same name in hadoop-common. Modified
to accommodate changes to HBase's CodecPool.
hbase-common/src/test/java/org/apache/hadoop/hbase/io/compress/TestCodecPool.java