Set the release date for 2.7.4.

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

@@ -15,7 +15,7 @@ Release 2.7.5 - UNRELEASED
     HADOOP-14702. Fix formatting issue and regression caused by conversion from
     APT to Markdown. (Doris Gu via iwasakims)
 
-Release 2.7.4 - UNRELEASED
+Release 2.7.4 - 2017-08-04
 
   INCOMPATIBLE CHANGES
 

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

@@ -1,6 +1,18 @@
 Hadoop HDFS Change Log
 
-Release 2.7.4 - UNRELEASED
+Release 2.7.5 - UNRELEASED
+
+  INCOMPATIBLE CHANGES
+
+  NEW FEATURES
+
+  IMPROVEMENTS
+
+  OPTIMIZATIONS
+
+  BUG FIXES
+
+Release 2.7.4 - 2017-08-04
 
   INCOMPATIBLE CHANGES
 

hadoop-mapreduce-project/CHANGES.txt

@@ -1,6 +1,18 @@
 Hadoop MapReduce Change Log
 
-Release 2.7.4 - UNRELEASED
+Release 2.7.5 - UNRELEASED
+
+  INCOMPATIBLE CHANGES
+
+  NEW FEATURES
+
+  IMPROVEMENTS
+
+  OPTIMIZATIONS
+
+  BUG FIXES
+
+Release 2.7.4 - 2017-08-04
 
   INCOMPATIBLE CHANGES
 

hadoop-yarn-project/CHANGES.txt

@@ -1,6 +1,18 @@
 Hadoop YARN Change Log
 
-Release 2.7.4 - UNRELEASED
+Release 2.7.5 - UNRELEASED
+
+  INCOMPATIBLE CHANGES
+
+  NEW FEATURES
+
+  IMPROVEMENTS
+
+  OPTIMIZATIONS
+
+  BUG FIXES
+
+Release 2.7.4 - 2017-08-04
 
   INCOMPATIBLE CHANGES