Avoid throw SocketException(10057) in TcpSocketChannel.DoClose when the Socket is not connected (#508)

src/DotNetty.Transport/Channels/Sockets/TcpSocketChannel.cs

@@ -170,9 +170,12 @@ namespace DotNetty.Transport.Channels.Sockets
         {
             try
             {
-                if (this.TryResetState(StateFlags.Open | StateFlags.Active))
+                if (this.TryResetState(StateFlags.Open))
                 {
-                    this.Socket.Shutdown(SocketShutdown.Both);
+                    if (this.TryResetState(StateFlags.Active))
+                    {
+                        this.Socket.Shutdown(SocketShutdown.Both);
+                    }
                     this.Socket.Dispose();
                 }
             }