Add missing CHANGES.txt entry for HDFS-8767 for branch-2.6

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

@@ -32,6 +32,9 @@ Release 2.6.4 - UNRELEASED
     HDFS-9600. do not check replication if the block is under construction
     (Phil Yang via vinayakumarb)
 
+    HDFS-8767. RawLocalFileSystem.listStatus() returns null for UNIX pipefile.
+    (Kanaka Kumar Avvaru via wheat9)
+
 Release 2.6.3 - 2015-12-17
 
   INCOMPATIBLE CHANGES