Add 2.7.3 release to CHANGES.txt

(cherry picked from commit 0383a3973b3b734fb23c331a2256dc92cff05365)

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

@@ -791,6 +791,18 @@ Release 2.8.0 - UNRELEASED
     HADOOP-12484. Single File Rename Throws Incorrectly In Potential Race
     Condition Scenarios. (Gaurav Kanade via cnauroth)
 
+Release 2.7.3 - UNRELEASED
+
+  INCOMPATIBLE CHANGES
+
+  NEW FEATURES
+
+  IMPROVEMENTS
+
+  OPTIMIZATIONS
+
+  BUG FIXES
+
 Release 2.7.2 - UNRELEASED
 
   INCOMPATIBLE CHANGES

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

@@ -1388,6 +1388,18 @@ Release 2.8.0 - UNRELEASED
     HDFS-9351. checkNNStartup() need to be called when fsck calls
     FSNamesystem.getSnapshottableDirs(). (Xiao Chen via Yongjun Zhang)
 
+Release 2.7.3 - UNRELEASED
+
+  INCOMPATIBLE CHANGES
+
+  NEW FEATURES
+
+  IMPROVEMENTS
+
+  OPTIMIZATIONS
+
+  BUG FIXES
+
 Release 2.7.2 - UNRELEASED
 
   INCOMPATIBLE CHANGES

hadoop-mapreduce-project/CHANGES.txt

@@ -338,6 +338,18 @@ Release 2.8.0 - UNRELEASED
    MAPREDUCE-6515. Update Application priority in AM side from AM-RM heartbeat
    (Sunil G via jlowe)
 
+Release 2.7.3 - UNRELEASED
+
+  INCOMPATIBLE CHANGES
+
+  NEW FEATURES
+
+  IMPROVEMENTS
+
+  OPTIMIZATIONS
+
+  BUG FIXES
+
 Release 2.7.2 - UNRELEASED
 
   INCOMPATIBLE CHANGES

hadoop-yarn-project/CHANGES.txt

@@ -990,6 +990,18 @@ Release 2.8.0 - UNRELEASED
     YARN-4326. Fix TestDistributedShell timeout as AHS in MiniYarnCluster no longer 
     binds to default port 8188. (Meng Ding via wangda)
 
+Release 2.7.3 - UNRELEASED
+
+  INCOMPATIBLE CHANGES
+
+  NEW FEATURES
+
+  IMPROVEMENTS
+
+  OPTIMIZATIONS
+
+  BUG FIXES
+
 Release 2.7.2 - UNRELEASED
 
   INCOMPATIBLE CHANGES