HDFS test builds always fails

[王磊]

Hi, I found some tests always fails in some pull requests such as
hadoop.hdfs.protocol.TestBlockListAsLongs of HDFS-17391
<https://github.com/apache/hadoop/pull/6594>. It should be caused by some
recent modification. It is suspected that the relevant modification is
HADOOP-19069 <https://github.com/apache/hadoop/pull/6541/files>. Who can
help solve this problem?