ChannelOperations#isDisposed should check for channel active

If the channel is no more active then this ChannelOperations is disposed.

src/main/java/reactor/ipc/netty/channel/ChannelOperations.java

@@ -195,7 +195,7 @@ public void dispose() {
 
 	@Override
 	public final boolean isDisposed() {
-		return get(channel()) != this;
+		return !channel().isActive() || get(channel()) != this;
 	}
 
 	@Override