Ansible complains about the following:

  [WARNING]: Found both group and host with same name: master

As the hostname is "master", rename the group to "masters" (with "s",
even though there is only one).

Signed-off-by: Niels de Vos <ndevos@redhat.com>

Ansible complains that 'include' is deprecated:

    [DEPRECATION WARNING]: The use of 'include' for tasks has been deprecated. Use
    'import_tasks' for static inclusions or 'include_tasks' for dynamic inclusions.
    This feature will be removed in a future release. Deprecation warnings can be
    disabled by setting deprecation_warnings=False in ansible.cfg.

Instead of 'include', use 'include_tasks'.

Signed-off-by: Niels de Vos <ndevos@redhat.com>

Ansible complains that checking the return value of a filter action is
deprecated. It seems required to use "is" instead of the pipe ("|").

    [DEPRECATION WARNING]: Using tests as filters is deprecated. Instead of using
    `result|version_compare` use `result is version_compare`. This feature will be
    removed in version 2.9. Deprecation warnings can be disabled by setting
    deprecation_warnings=False in ansible.cfg.

Signed-off-by: Niels de Vos <ndevos@redhat.com>