Fixed issue: NETTY-205 Unnecessary exception log on early disconnection

* Do not log ClosedChannelException in RegisterTask.run()

src/main/java/org/jboss/netty/channel/socket/nio/NioWorker.java

@@ -751,9 +751,11 @@ class NioWorker implements Runnable {
                     future.setFailure(e);
                 }
                 close(channel, succeededFuture(channel));
+                if (!(e instanceof ClosedChannelException)) {
                     throw new ChannelException(
                             "Failed to register a socket to the selector.", e);
                 }
+            }
 
             if (!server) {
                 if (!((NioClientSocketChannel) channel).boundManually) {