public static Compressor getCompressor(CompressionCodec codec) {
    return getCompressor(codec, null);
  }
Get a {@link Compressor} for the given {@link CompressionCodec} from the pool, or get a new one
if the pool is empty. Copied from hadoop-common without significant modification.
hbase-common/src/main/java/org/apache/hadoop/hbase/io/compress/CodecPool.java