Change all references to the container ID in pkg/kubelet/... to the
strong type defined in pkg/kubelet/container: ContainerID
The motivation for this change is to make the format of the ID
unambiguous, specifically whether or not it includes the runtime
prefix (e.g. "docker://").
Each container with a readiness has an individual go-routine which
handles periodic probing for that container. The results are cached, and
written to the status.Manager in the pod sync path.
Add an experimental network plugin implementation named "cni" that
uses the Container Networking Interface (CNI) specification for
configuring networking for pods.
https://github.com/appc/cni/blob/master/SPEC.md
