CentOS 7 provides up to date Ansible with really old jinja version

Signed-off-by: Etienne Champetier <e.champetier@ateme.com>

We have multiple breakage report with Ansible 2.10+ in https://github.com/kubernetes-sigs/kubespray/issues/6762


README.md already recommended 2.9+

Signed-off-by: Etienne Champetier <champetier.etienne@gmail.com>

* bump minimal ansible version to 2.8.0

* check ansible version in separate playbook