HADOOP-16643. Update netty4 to the latest 4.1.42. Contributed by Lisheng Sun.

hadoop-project/pom.xml

@@ -843,7 +843,7 @@
       <dependency>
         <groupId>io.netty</groupId>
         <artifactId>netty-all</artifactId>
-        <version>4.0.52.Final</version>
+        <version>4.1.42.Final</version>
       </dependency>
 
       <dependency>