[k8s] Allow cancel autostop for cluster on k8s (#3525)

* Allow autodown for k8s

* k8s allow cancel

sky/backends/cloud_vm_ray_backend.py

@@ -4066,7 +4066,7 @@ def set_autostop(self,
         if idle_minutes_to_autostop is not None:
             # Skip auto-stop for Kubernetes clusters.
             if (isinstance(handle.launched_resources.cloud, clouds.Kubernetes)
-                    and not down):
+                    and not down and idle_minutes_to_autostop >= 0):
                 # We should hit this code path only for the jobs controller on
                 # Kubernetes clusters.
                 assert (controller_utils.Controllers.from_name(