When enable_network_policy is set to True with Calico 3 kubectl
apply fails with the error:

The Deployment "calico-kube-controllers" is invalid:
spec.strategy.rollingUpdate: Forbidden: may not be specified when
strategy type is 'Recreate'

See

https://github.com/kubernetes-incubator/kubespray/issues/3267

Changing the update strategy to RollingUpdate avoids this error.