kubelet: moving the kubelet to rkt

[philips]

The kubelet and kubernetes control plane have issues being updated independently. So, we should pull the kubelet out of the CoreOS image and instead run it inside of rkt so that users have the flexibility of upgrading it with their control plane instead of their OS.

This is a tracking issue to get all of this work over the finish line.

container/rkt issues

• rkt fly and stage 1 upgrades must make it into CoreOS release: stage1: configuration and defaults rkt/rkt#1425
• resolv.conf for the kubelet
  • rkt: /etc/resolv.conf doesn't get populated rkt/rkt#660

configuration and documentation

• kubelet "version decider" logic, design doc
• kubelet version decider documentation and workflow docs

[philips]

cc @crawford @aaronlevy @pbx0 @jonboulle @steveej Please take a look at let me know if more stuff needs to be added here.

[aaronlevy]

WIP: hyperkube image build: coreos/coreos-kubernetes#228
WIP: kubelet.service unit (running via rkt-fly): coreos/coreos-overlay#1706

[aaronlevy]

WIP: reference implementation of a "version-controller" application which drives kubelet versions based on api-server updates: coreos/coreos-kubernetes#249

[peebs]

WIP kubelet agent: coreos/coreos-kubernetes#246
WIP kubelet.service: coreos/coreos-overlay#1726

[crawford]

This was finished a while ago. I lost track of this issue.