Remove references to unsupported operating systems

All references to Gentoo, SUSE, Debian stretch and Centos-7  are removed.
Conditional tasks, ternary operators and variables are simplified where possible
OS specific variables files are generalised where possible

Change-Id: I4153df38980650c726cc1a79320b22e1e07605cf

meta/main.yml

@@ -22,14 +22,11 @@ galaxy_info:
   platforms:
     - name: Debian
       versions:
-        - stretch
+        - buster
     - name: Ubuntu
       versions:
-        - xenial
         - bionic
-    - name: opensuse
-      versions:
-        - 15
+        - focal
   categories:
     - cloud
     - development

tasks/octavia_install.yml

@@ -16,7 +16,7 @@
   package:
     name: "{{ octavia_package_list }}"
     state: "{{ octavia_package_state }}"
-    update_cache: "{{ (ansible_pkg_mgr in ['apt', 'zypper']) | ternary('yes', omit) }}"
+    update_cache: "{{ (ansible_pkg_mgr == 'apt') | ternary('yes', omit) }}"
     cache_valid_time: "{{ (ansible_pkg_mgr == 'apt') | ternary(cache_timeout, omit) }}"
   register: install_packages
   until: install_packages is success

vars/redhat.yml

@@ -28,7 +28,7 @@ octavia_service_distro_packages:
   - openstack-octavia-health-manager
   - openstack-octavia-housekeeping
   - openstack-octavia-worker
-  - "{{ ansible_distribution_major_version is version('8', '<') | ternary('systemd-python', 'python3-systemd') }}"
+  - python3-systemd
 
 octavia_distro_openstack_clients_packages:
   - python-shade

vars/suse.yml

@@ -1,22 +0,0 @@
----
-# Copyright 2019, SUSE Linux GmbH
-#
-# Licensed under the Apache License, Version 2.0 (the "License");
-# you may not use this file except in compliance with the License.
-# You may obtain a copy of the License at
-#
-#     http://www.apache.org/licenses/LICENSE-2.0
-#
-# Unless required by applicable law or agreed to in writing, software
-# distributed under the License is distributed on an "AS IS" BASIS,
-# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-# See the License for the specific language governing permissions and
-# limitations under the License.
-
-octavia_distro_packages:
-  - iptables
-  - libxml2-devel
-  - git-core
-
-octavia_devel_distro_packages:
-  - systemd-devel