net/virtio-user: fix feature setting with vhost-net backend

net/virtio-user: fix feature setting with vhost-net backend

When the backend is vhost-net, virtio-user must work in client mode and
needs to request features from the backend in virtio_user_dev_init().
But currently, virtio-user is assigned to default features in this case.

This patch is to fix this inappropriate feature setting.

Fixes: bd8f50a45d0f ("net/virtio-user: support server mode")

Signed-off-by: Jiayu Hu <jiayu.hu@intel.com>
Tested-by: Lei Yao <lei.a.yao@intel.com>
Reviewed-by: Tiwei Bie <tiwei.bie@intel.com>
Reviewed-by: Zhiyong Yang <zhiyong.yang@intel.com>