HDFS-16385. Fix Datanode retrieve slownode information bug. (#3803)

Reviewed-by: Symious <yiyang0203@gmail.com>
Reviewed-by: Hui Fei <ferhui@apache.org>
Reviewed-by: litao <tomleescut@gmail.com>

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/protocolPB/DatanodeProtocolServerSideTranslatorPB.java

@@ -152,6 +152,7 @@ public class DatanodeProtocolServerSideTranslatorPB implements
     }
 
     builder.setFullBlockReportLeaseId(response.getFullBlockReportLeaseId());
+    builder.setIsSlownode(response.getIsSlownode());
     return builder.build();
   }