HDFS-15465: Support WebHDFS accesses to the data stored in secure Datanode through insecure Namenode

[vitojeng]

Sqoop 執行時發生的錯誤:

org.apache.hadoop.HadoopIllegalArgumentException: Invalid argument, newValue is null

可能原因與 HDFS-15645 相同, 需要在 hadoop 3.2.2 上測試驗證.
PR: apache#2135