Automatic merge from submit-queue. If you want to cherry-pick this change to another branch, please follow the instructions <a href="https://github.com/kubernetes/community/blob/master/contributors/devel/cherry-picks.md">here</a>.
Add a file store utility package in kubelet
More and more components checkpoints (i.e., persist their states) in
kubelet. Refurbish and move the implementation in dockershim to a
utility package to improve code reusability.