Upgrade Netty 3.9.2, close AsyncHttpClient#568

Author: Stephane Landelle

pom.xml

@@ -81,7 +81,7 @@
         <dependency>
             <groupId>io.netty</groupId>
             <artifactId>netty</artifactId>
-            <version>3.9.1.Final</version>
+            <version>3.9.2.Final</version>
         </dependency>
 
         <dependency>