cgroups resources need update

[runcom]

running a container with the default {runtime,config}.json from runc spec fails because swappiness is set by default to -1

$ sudo ./bin/ctr containers start test2 `pwd`
[ctr] rpc error: code = 2 desc = "unmarshal /home/runcom/src/github.com/docker/containerd/runtime.json: json: cannot unmarshal number -1 into Go value of type uint64"

Fix depends on opencontainers/runtime-spec#233 which will have nullable values for other cgroup values as well

[crosbymichael]

Ya,, for now you can just delete that field in the runtime. If you look in the docs dir and the bundle.md file I think i make some edits in the examples.

[runcom]

@crosbymichael did that, I opened this as a reminder

[runcom]

I'm updating runc/libcontainer to the new spec with pointers which got merged, ongoing work is here https://github.com/runcom/runc/commits/update-specs
if you are already working on it I'll stop

he was faster than me opencontainers/runc#444