HADOOP-14992. Upgrade Avro patch version. Contributed by Bharat Viswanadham

hadoop-project/pom.xml

@@ -65,7 +65,7 @@
     <java.security.egd>file:///dev/urandom</java.security.egd>
 
     <!-- avro version -->
-    <avro.version>1.7.4</avro.version>
+    <avro.version>1.7.7</avro.version>
 
     <!-- jersey version -->
     <jersey.version>1.19</jersey.version>