Automatic merge from submit-queue

kubectl rolling-update support for same image

Fixes #23497.

Enables `kubectl rolling-update --image` to the same image, adding a `--image-pull-policy` flag to remove ambiguity. This allows rolling-update to behave as an "update and/or restart" (https://github.com/kubernetes/kubernetes/issues/23497#issuecomment-212349730), or as a forced update when the same tag can mean multiple versions (e.g. `:latest`). cc @janetkuo @nikhiljindal