Fixed issue: NETTY-25 (Unnecessarily logged exception in the blocking I/O server socket)

* Suppressed the expected exception logging

src/main/java/org/jboss/netty/channel/socket/oio/OioServerSocketPipelineSink.java

@@ -216,6 +216,12 @@ class OioServerSocketPipelineSink extends AbstractChannelSink {
                 } catch (SocketTimeoutException e) {
                     // Thrown every second to stop when requested.
                 } catch (IOException e) {
+                    // Don't log the exception if the server socket was closed
+                    // by a user.
+                    if (!channel.isBound()) {
+                        break;
+                    }
+
                     logger.warn(
                             "Failed to accept a connection.", e);
                     try {