Updated CHANGES.txt to reflect hadoop-2.6.0 release dates.

(cherry picked from commit 770cc144425b6188d9b93178c77a35cd830a60df)

hadoop-common-project/hadoop-common/CHANGES.txt

@@ -1,6 +1,6 @@
 Hadoop Change Log
 
-Release 2.6.0 - UNRELEASED
+Release 2.6.0 - 2014-11-15
 
   INCOMPATIBLE CHANGES
 

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

@@ -1,6 +1,6 @@
 Hadoop HDFS Change Log
 
-Release 2.6.0 - UNRELEASED
+Release 2.6.0 - 2014-11-15
 
   INCOMPATIBLE CHANGES
 

hadoop-mapreduce-project/CHANGES.txt

@@ -1,6 +1,6 @@
 Hadoop MapReduce Change Log
 
-Release 2.6.0 - UNRELEASED
+Release 2.6.0 - 2014-11-15
 
   INCOMPATIBLE CHANGES
 

hadoop-yarn-project/CHANGES.txt

@@ -1,6 +1,6 @@
 Hadoop YARN Change Log
 
-Release 2.6.0 - UNRELEASED
+Release 2.6.0 - 2014-11-15
 
   INCOMPATIBLE CHANGES