fix k3s upgrade-plan

systemd/graduated/k3s/upgrade-plan.yaml

@@ -17,3 +17,26 @@ spec:
   upgrade:
     image: rancher/k3s-upgrade
   channel: https://update.k3s.io/v1-release/channels/stable
+---
+# Agent plan
+apiVersion: upgrade.cattle.io/v1
+kind: Plan
+metadata:
+  name: agent-plan
+  namespace: system-upgrade
+spec:
+  concurrency: 1
+  cordon: true
+  nodeSelector:
+    matchExpressions:
+    - key: node-role.kubernetes.io/control-plane
+      operator: DoesNotExist
+  prepare:
+    args:
+    - prepare
+    - server-plan
+    image: rancher/k3s-upgrade
+  serviceAccountName: system-upgrade
+  upgrade:
+    image: rancher/k3s-upgrade
+  channel: https://update.k3s.io/v1-release/channels/stable