move previous change log to the end of the section rather than the beginning

git-svn-id: https://svn.apache.org/repos/asf/hadoop/core/trunk@633283 13f79535-47bb-0310-9956-ffa450edef68

CHANGES.txt

@@ -40,9 +40,6 @@ Trunk (unreleased changes)
 
   IMPROVEMENTS
 
-    HADOOP-2833. Do not use "Dr. Who" as the default user in JobClient. 
-    A valid user name is required. (Tsz Wo (Nicholas), SZE via rangadi)
-
     HADOOP-2655. Copy on write for data and metadata files in the 
     presence of snapshots. Needed for supporting appends to HDFS
     files. (dhruba) 
@@ -59,6 +56,9 @@ Trunk (unreleased changes)
     HADOOP-910. Enables Reduces to do merges for the on-disk map output files 
     in parallel with their copying. (Amar Kamat via ddas)
 
+    HADOOP-2833. Do not use "Dr. Who" as the default user in JobClient. 
+    A valid user name is required. (Tsz Wo (Nicholas), SZE via rangadi)
+
   OPTIMIZATIONS
 
     HADOOP-2790.  Fixed inefficient method hasSpeculativeTask by removing