Bump Ansible version range to 2.8 - 2.9

Updates the minimum version of Ansible from 2.6 to 2.8, and the maximum
supported version from 2.8 to 2.9.

CentOS 8 requires Ansible 2.8.

Change-Id: I3f8f7f8d7d37e3cb851965a491ac9c43030869d5
Story: 2006574
Task: 38826

ansible/roles/kolla-ansible/templates/requirements.txt.j2

@@ -7,7 +7,7 @@ kolla-ansible=={{ kolla_openstack_release }}
 {% endif %}
 # Limit the version of ansible used by kolla-ansible to avoid new releases from
 # breaking tested code. Changes to this limit should be tested.
-ansible>=2.6,<2.9
+ansible>=2.8,<2.10
 {% if ansible_os_family == 'RedHat' and ansible_distribution_major_version | int >= 8 %}
 selinux
 {% endif %}

releasenotes/notes/ansible-2.8-2.9-2df006b066704417.yaml

+---
+upgrade:
+  - |
+    Updates the minimum supported version of Ansible from 2.6 to 2.8, and the
+    maximum supported version from 2.8 to 2.9. This is true for both Kayobe and
+    Kolla Ansible.

requirements.txt

@@ -3,7 +3,7 @@
 # process, which may cause wedges in the gate later.
 
 pbr>=2.0 # Apache-2.0
-ansible>=2.6.0,<2.9.0 # GPLv3
+ansible>=2.8.0,<2.10.0 # GPLv3
 cliff>=2.5.0,<2.15.0 # Apache
 netaddr!=0.7.16,>=0.7.13 # BSD
 PyYAML>=3.10.0 # MIT