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: Id400c679e1ccc5cc10a92143321ec3e182f9ecdc

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
+        - 8
-    - name: opensuse
-      versions:
-        - 15
   categories:
     - cloud
     - python

tasks/mistral_install.yml

@@ -61,7 +61,7 @@
   package:
     name: "{{ mistral_package_list }}"
     state: "{{ mistral_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

@@ -24,7 +24,7 @@ mistral_service_distro_packages:
   - openstack-mistral-engine
   - openstack-mistral-executor
   - openstack-mistral-notifier
-  - "{{ ansible_distribution_major_version is version('8', '<') | ternary('systemd-python', 'python3-systemd') }}"
+  - python3-systemd
 
 mistral_oslomsg_amqp1_distro_packages:
   - cyrus-sasl-lib

vars/suse.yml

@@ -1,29 +0,0 @@
----
-# Copyright 2019, VEXXHOST, Inc.
-#
-# 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.
-
-mistral_devel_distro_packages:
-  - git
-  - systemd-devel
-
-mistral_distro_packages: []
-
-mistral_service_distro_packages:
-  - openstack-mistral
-  - python-systemd
-
-mistral_oslomsg_amqp1_distro_packages:
-  - cyrus-sasl
-  - cyrus-sasl-plain
-  - cyrus-sasl-digestmd5