[#670] Intermittent IllegalStateException with ByteToMessageDecoder impl with bounded inbound buffer

* AioSocketChannel.expandReadBuffer() should not call discardReadBytes()
becuase it messes up with NIO.2

transport/src/main/java/io/netty/channel/socket/aio/AioSocketChannel.java

@@ -192,7 +192,6 @@ public class AioSocketChannel extends AbstractAioChannel implements SocketChanne
 
         final int maxCapacity = byteBuf.maxCapacity();
         if (capacity == maxCapacity) {
-            byteBuf.discardReadBytes();
             return;
         }