net/virtio-user: do not reset owner when driver resets

net/virtio-user: do not reset owner when driver resets

When driver resets the device, virtio-user just needs to send
GET_VRING_BASE messages to stop the vhost backend, and that's
what QEMU does. With this change, we won't need to set owner
when starting virtio-user device anymore. This will help us to
get rid of below error message on startup:

vhost_kernel_ioctl(): VHOST_SET_OWNER failed: Device or resource busy

Fixes: bce7e9050f9b ("net/virtio-user: fix start with kernel vhost")
Fixes: 0d6a8752ac9d ("net/virtio-user: fix crash as features change")
Cc: stable@dpdk.org
Signed-off-by: Tiwei Bie <tiwei.bie@intel.com>
Reviewed-by: Maxime Coquelin <maxime.coquelin@redhat.com>