runtime-rs: Pass the vhost-user-net device id to dragonball

Dragonball now identifies every network device by its iface_id and
refuses a device without one, so pass the endpoint's dev_id through
explicitly instead of leaving the field to its empty default. This
completes the change started two commits back: every network backend
hands dragonball a device name the runtime knows.

Signed-off-by: Xuewei Niu <niuxuewei.nxw@antgroup.com>

src/runtime-rs/crates/hypervisor/src/dragonball/inner_device.rs

@@ -358,8 +358,8 @@ impl DragonballInner {
             num_queues: Some(num_queues),
             queue_size: Some(config.queue_size as u16),
             backend: dragonball::api::v1::Backend::VhostUser(DragonballVhostUserConfig {
+                iface_id: config.dev_id.clone(),
                 sock_path: config.socket_path.clone(),
-                ..Default::default()
             }),
             guest_mac,
             use_shared_irq: None,