Only set socket send and receive buffer sizes if it is in the Remoting subsystem configuration

Original report:

In our testing of Wildfy 10 CR4, in the performance lab, we found that one of the differences between EAP 6.4.x and Wildfly 10 was that EAP does not set the socket send and receive buffers. We changed the configuration of Wildfly (Undertow) to remove the buffer parameters from the configuration, and we found that the buffer sizes were still be set to 8k. We hacked XNIO to comment out the setting of these parameters, and latency improved quite a bit.

So, we need a permanent fix so that the socket send and receive buffers are only set, if they are specified in the configuration.

This applies to the Remoting subsystem configuration, versions 2.0 and onwards, and also possibly to Undertow, though that subsystem does not appear to use default values.