我有以下复制控制器在Kubernetes上的GKE:

apiVersion: v1
kind: ReplicationController
metadata:
  name: myapp
  labels:
    app: myapp
spec:
  replicas: 2
  selector:
    app: myapp
    deployment: initial
  template:
    metadata:
      labels:
        app: myapp
        deployment: initial
    spec:
      containers:
      - name: myapp
        image: myregistry.com/myapp:5c3dda6b
        ports:
        - containerPort: 80
      imagePullPolicy: Always
      imagePullSecrets:
        - name: myregistry.com-registry-key

现在，如果我说

kubectl rolling-update myapp --image=us.gcr.io/project-107012/myapp:5c3dda6b

执行滚动更新，但不重新拉取。为什么?