CHANGES.txt: add YARN-2977

(cherry picked from commit 76b0370a27c482caff9498e15ef889d37f413ce7)

Conflicts:
	hadoop-yarn-project/CHANGES.txt

hadoop-yarn-project/CHANGES.txt

@@ -1,5 +1,20 @@
 Hadoop YARN Change Log
 
+Release 2.6.1 - Unreleased
+
+  INCOMPATIBLE CHANGES
+
+  NEW FEATURES
+
+  IMPROVEMENTS
+
+  OPTIMIZATIONS
+
+  BUG FIXES
+
+    YARN-2977. Fixed intermittent TestNMClient failure.
+    (Junping Du via ozawa)
+
 Release 2.6.0 - 2014-11-18
 
   INCOMPATIBLE CHANGES