HDFS-6576. Datanode log is generating at root directory in security mode (Contributed by surendra singh lilhore)

Just merging CHANGES.txt changes from branch-2 to keep in sync.

(cherry picked from commit a87ab77fec375c02ba507bd7c7ca1e0082f623c2)

Conflicts:
	hadoop-common-project/hadoop-common/src/main/conf/hadoop-env.sh

hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt

@@ -687,6 +687,9 @@ Release 2.8.0 - UNRELEASED
     HDFS-8209. Support different number of datanode directories in MiniDFSCluster.
     (surendra singh lilhore via vinayakumarb)
 
+    HDFS-6576. Datanode log is generating at root directory in security mode
+    (surendra singh lilhore via vinayakumarb)
+
 Release 2.7.1 - UNRELEASED
 
   INCOMPATIBLE CHANGES