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: Id4f43e11bb02733b90f8bdf49e86f7a37656c68f

meta/main.yml

@@ -22,17 +22,14 @@ galaxy_info:
   platforms:
     - name: Debian
       versions:
-        - stretch
+        - buster
     - name: Ubuntu
       versions:
-        - xenial
         - bionic
+        - focal
     - name: EL
       versions:
-        - 7
-    - name: opensuse
-      versions:
-        - 15
+        - 8
   categories:
     - cloud
     - python

tasks/glance_install.yml

@@ -117,7 +117,7 @@
   package:
     name: "{{ glance_package_list }}"
     state: "{{ glance_package_state }}"
-    update_cache: "{{ (ansible_facts['pkg_mgr'] in ['apt', 'zypper']) | ternary('yes', omit) }}"
+    update_cache: "{{ (ansible_facts['pkg_mgr'] == 'apt') | ternary('yes', omit) }}"
     cache_valid_time: "{{ (ansible_facts['pkg_mgr'] == 'apt') | ternary(cache_timeout, omit) }}"
   register: install_packages
   until: install_packages is success

vars/redhat.yml

@@ -26,7 +26,7 @@ glance_devel_distro_packages:
 
 glance_service_distro_packages:
   - openstack-glance
-  - "{{ ansible_facts['distribution_major_version'] is version('8', '<') | ternary('systemd-python', 'python3-systemd') }}"
+  - python3-systemd
 
 glance_oslomsg_amqp1_distro_packages:
   - cyrus-sasl-lib

vars/suse.yml

@@ -1,36 +0,0 @@
----
-# Copyright 2016, Intel Corporation.
-# Copyright 2017, 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.
-
-glance_distro_packages:
-  - git-core
-  - nfs-utils
-  - libxslt1
-  - rpcbind
-  - cron
-
-glance_devel_distro_packages:
-  - libxml2-devel
-  - systemd-devel
-
-glance_service_distro_packages:
-  - openstack-glance
-  - openstack-glance-api
-  - python-systemd
-
-glance_oslomsg_amqp1_distro_packages:
-  - cyrus-sasl
-  - cyrus-sasl-plain
-  - cyrus-sasl-digestmd5