Add a missing close(SelectionKey) call

* Without calling close(SelectionKey), the client boss loop can fall
into an infinite loop.

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

@@ -372,6 +372,7 @@ class NioClientSocketPipelineSink extends AbstractChannelSink {
             ConnectException cause = null;
             for (SelectionKey k: keys) {
                 if (!k.isValid()) {
+                    close(k);
                     continue;
                 }