virtio-devices: Use VirtioCommon::spawn_worker()

Replace use of spawn_virtio_thread() helper with the new method on
VirtioCommon to handle thread management as well as spawning. As a
result this cleanly handles reset if it fails to spawn the thread.

Assisted-by: Claude:Opus-4.7
Signed-off-by: Rob Bradford <rbradford@meta.com>

virtio-devices/src/rng.rs

@@ -29,7 +29,6 @@ use super::{
     VirtioCommon, VirtioDevice, VirtioDeviceType,
 };
 use crate::seccomp_filters::Thread;
-use crate::thread_helper::spawn_virtio_thread;
 use crate::{GuestMemoryMmap, VirtioInterrupt, VirtioInterruptType};
 
 const QUEUE_SIZE: u16 = 256;
@@ -287,20 +286,16 @@ impl VirtioDevice for Rng {
 
             let paused = self.common.paused.clone();
             let paused_sync = self.common.paused_sync.clone();
-            let mut epoll_threads = Vec::new();
-            spawn_virtio_thread(
+            self.common.spawn_worker(
                 &self.id,
                 &self.seccomp_action,
                 Thread::VirtioRng,
-                &mut epoll_threads,
                 &self.exit_evt,
                 device_status.clone(),
                 interrupt_cb.clone(),
                 move || handler.run(&paused, paused_sync.as_ref().unwrap()),
             )?;
 
-            self.common.epoll_threads = Some(epoll_threads);
-
             event!("virtio-device", "activated", "id", &self.id);
             return Ok(());
         }