Replace deprecated env vars passed to the kubelet-wrapper

[carolynvs]

This fixes #207.

The following environment variables used by kubelet-wrapper have been
deprecated:

• KUBELET_VERSION has been replaced with KUBELET_IMAGE_TAG
• KUBELET_ACI has replaced with KUBELET_IMAGE_URL
• RKT_OPTS has been replaces with RKT_RUN_ARGS

See https://github.com/coreos/coreos-overlay/blob/build-1220/app-admin/kubelet-wrapper/files/kubelet-wrapper#L29-L39.

[ghost]

Can one of the admins verify this patch?

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[peebs]

ok to test

[carolynvs]

I signed it!

[carolynvs]

@pbx0 CLA is signed and this is ready for review. Thanks!

[aaronlevy]

@carolynvs thank you for fixing this!

Would it work for you to hold off on getting this merged until closer to the k8s v1.6.0 release (end of March-ish)? The reason I ask is that I know there are some installations that base decisions off these values - and changing it mid-minor-release might cause some headaches.

I was hoping to get changes like this, and #246, wrapped into the bootkube release containting v1.6.0, as that provides a pretty clear upgrade line for existing users.

[aaronlevy]

@carolynvs actually, ignore my previous comment - for some reason I was thinking we were generating the kubelet service file, but this is just updating the hack/documentation examples - which shouldn't affect existing users.

Let me run a quick test on this and see if we can get it merged.

[aaronlevy]

lgtm, thanks for the fix!