Stabilize role w.r.t new Ansible 2.10 semantics, various fixes & prevent configuration to be generated several times
- Ansible 2.10 fails fast when undefined values are encountered in expressions. Catch these values and set them to something meaningful so that Ansible does not choke.
- Add files to manage devices in cgroups (useful for gpus)
- Enable additional cgroup support at boot
- Configuration is generated only once, for each node if cache mode is not used, or when it is used only once and for all nodes