Add health checking for the kubelet & container runtime

[mrIncompetent]

We should implement the same kind of health checking for the kubelet & the containerruntime like Google does with the container-optimized images:
https://github.com/kubernetes/kubernetes/blob/master/cluster/gce/gci/health-monitor.sh

[mrIncompetent]

This could have potentially prevented the issue @pkavajin ran into

[mrIncompetent]

#343 (comment)