Improve node bootstrap time with node-authorizer and protokube in s3

[akursell-wish]

When using node-authorizer and a protokube image that must be pulled via http, node bootstrap takes more than 5 minutes because the order of dependencies is screwed up. What happens is:

• kops starts protokube, node-authorizer, and kubelet at the same time
• protokube cannot start until the protokube image is pulled, node-authorizer fails because protokube has not added the master ips to /etc/hosts, and kubelet fails because node-authorizer hasn't completed its task
• After a minute or two, kops notices the failure, finally starts the LoadImage.protokube task that loads protokube, and restarts node-authorizer
• node-authorizer fails again because protokube is still being pulled
• protokube is pulled and is started
• node-authorizer, after another minute or two, is restarted again by kops and succeeds
• kubelet finally succeeds and the node joins the cluster

With this patch:

• The protokube image is loaded first, before the protokube, node-authorizer, or kubelet services are
• node-authorizer continuously retries until it succeeds

Node bootstrap now takes ~2 minutes.

I have tested this patch, and it works at least in our setup, but I don't know if this is unsound in other configurations. In particular, I noticed that kops seemed to depend on node-authorizer either failing or succeeding to make progress. If we didn't load the protokube image before starting node-authorizer, kops would hang indefinitely and never bootstrap.