Fix compile errors with newer compilers.
Fix compile errors with newer compilers.
Only enable hotplug if host advertises it.
Increase NETKVM Rx/Tx buffer size.

By default, NETKVM post only 256 receive buffer while we virtio_queue advise 16384 queue size. Buffer can be easily run out if packet is coming in a fast rate. Especially when GRO is not enabled, we need a lot more buffer than our linux counterpart. It contributes to quite a bit for NTTTCP retransmission we have seen.