@Override
  public void close() {
    if (inputStream != null) {
      IOUtils.closeQuietly(inputStream);
      inputStream = null;
    }
  }
This is used to determine whether we have already reached the WALTrailer. As the size and magic
are at the end of the WAL file, it is possible that these two options are missing while
writing, so we will consider there is no trailer. And when we actually reach the WALTrailer, we
will try to decode it as WALKey and we will fail but the error could be varied as it is parsing
WALTrailer actually.
@return whether this is a WALTrailer and we should throw EOF to upper layer the file is done
hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/wal/AbstractProtobufWALReader.java