#1375 changed Resources.MemorySwap to a uint64.

https://github.com/opencontainers/runc/blob/master/libcontainer/configs/cgroup_unix.go#L53-L54

Comment on that field is set to -1 for unlimited, which can't be done with a uint64

This is blocking a vendored dep bump in kube: kubernetes/kubernetes#43856

@derekwaynecarr