vhost-user: Fix the virtio features negotiation flaw

vhost-user: Fix the virtio features negotiation flaw

This patch aims to fix unexpected negotiation features for
vhost-user netdev interface.

When openvswitch reconnect Qemu after an unexpected disconnection
and Qemu therefore start the vhost_dev, acked_features field in
vhost_dev is initialized with value fetched from acked_features
field in NetVhostUserState, which should be up-to-date at that
moment but Qemu could not make it actually during the time window
of virtio features negotiation.

So we save the acked_features right after being configured by
guest virtio driver so it can be used to restore acked_features
field in vhost_dev correctly.

Signed-off-by: Hyman Huang(黄勇) <huangy81@chinatelecom.cn>
Signed-off-by: Guoyi Tu <tugy@chinatelecom.cn>
Signed-off-by: Liuxiangdong <liuxiangdong5@huawei.com>
Message-Id: <b9f8cf5561a79ea65ea38960e5a5e6d3707eef0a.1671627406.git.huangy81@chinatelecom.cn>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>