Fix 'virtual_subtype' grain for kubernetes and libpod containers
Fix 'virtual_subtype' grain for kubernetes and libpod containers

All the containers started by kubelet (hence kubernetes) are assigned
to the `kubepods` cgroup slice (see [1]). That happens despite of the
Container Runtime Interface being used.

Containers started via tools using `libpod` [2] (eg: podman) are
assigned to the `libpod_parent` cgroup slice.

[1] https://github.com/kubernetes/community/blob/master/contributors/design-proposals/node/node-allocatable.md#recommended-cgroups-setup
[2] https://github.com/projectatomic/libpod

Signed-off-by: Flavio Castelli <d1035a58d87d0b7918844ad2fd699273faf2f5d5@suse.com>

saltstack/salt,saltstack/salt,saltstack/salt,saltstack/salt,saltstack/salt