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

(cherry picked from commit 85af77c75768416db24ca506fd1704ce664ca92f)

 Conflicts:
	hadoop-project/pom.xml

hadoop-project/pom.xml

@@ -133,7 +133,7 @@
     <htrace4.version>4.1.0-incubating</htrace4.version>
     <metrics.version>3.2.4</metrics.version>
     <netty3.version>3.10.6.Final</netty3.version>
-    <netty4.version>4.0.52.Final</netty4.version>
+    <netty4.version>4.1.42.Final</netty4.version>
 
     <!-- Maven protoc compiler -->
     <protobuf-maven-plugin.version>0.5.1</protobuf-maven-plugin.version>