Update CHANGES.txt for recent commits to 2.7 and 2.6

(cherry picked from commit c77c35f83ce953005fe0d3334acf0f0013a82139)

hadoop-yarn-project/CHANGES.txt

@@ -1179,6 +1179,9 @@ Release 2.7.3 - UNRELEASED
     YARN-4546. ResourceManager crash due to scheduling opportunity overflow.
     (Jason Lowe via junping_du)
 
+    YARN-3695. ServerProxy (NMProxy, etc.) shouldn't retry forever for non
+    network exception. (Raju Bairishetti via jianhe)
+
 Release 2.7.2 - UNRELEASED
 
   INCOMPATIBLE CHANGES
@@ -2039,6 +2042,12 @@ Release 2.6.4 - UNRELEASED
   YARN-4546. ResourceManager crash due to scheduling opportunity overflow.
   (Jason Lowe via junping_du)
 
+    YARN-3842. NMProxy should retry on NMNotYetReadyException. 
+    (Robert Kanter via kasha)
+
+    YARN-3695. ServerProxy (NMProxy, etc.) shouldn't retry forever for non
+    network exception. (Raju Bairishetti via jianhe)
+
 Release 2.6.3 - 2015-12-17
 
   INCOMPATIBLE CHANGES