* Override the default value of containerd's root, state, and oom_score configurations
* Add tests data for containerd_storage_dir, containerd_state_dir and containerd_oom_score variables
* containerd docker hub registry mirror support
* add docs
* fix typo
* fix yamllint
* fix indent in sample
and ansible-playbook param in testcases_run
* fix md
* mv common vars to tests/common/_docker_hub_registry_mirror.yml
* checkout vars to upgrade tests