vhost: Fix kthread worker cgroup failure handling

If we fail to attach to a cgroup we are leaking the id. This adds
a new goto to free the id.

Fixes: 7d9896e9f6d0 ("vhost: Reintroduce kthread API and add mode selection")
Signed-off-by: Mike Christie <[e-mail]>
Acked-by: Jason Wang <[e-mail]>
Reviewed-by: Chaitanya Kulkarni <[e-mail]>
Signed-off-by: Michael S. Tsirkin <[e-mail]>
Message-Id: <[e-mail]>

drivers/vhost/vhost.c

···
 
 	ret = vhost_attach_task_to_cgroups(worker);
 	if (ret)
-		goto stop_worker;
+		goto free_id;
 
 	worker->id = id;
 	return 0;
 
+free_id:
+	xa_erase(&dev->worker_xa, id);
 stop_worker:
 	vhost_kthread_do_stop(worker);
 	return ret;