hv_sock: disable SO_RCVLOWAT support

For Hyper-V it is quiet difficult to support this socket option,due to
transport internals, so disable it.

Signed-off-by: Arseniy Krasnov <AVKrasnov@sberdevices.ru>
Reviewed-by: Dexuan Cui <decui@microsoft.com>
Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>