Drop support for Ansible 2.8

[Richard Megginson]

Ansible 2.8 is EOL.
https://access.redhat.com/support/policy/updates/ansible-engine
The system roles team would like to drop support for Ansible 2.8.  This
means

* Change all meta/main.yml to use
galaxy_info:
  min_ansible_version: 2.9

* Change all CI testing to drop support for Ansible 2.8

* Change any README or other documentation that refers to support for
Ansible 2.8 or earlier

If there are any objections to this plan, please let me know ASAP.