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

Depends-On: Ic31fd78bb5ad9cd484f44e63ba02db7424a500d5
Change-Id: I7c6258673b7b13c15177873fb42080e452eba2d4

meta/main.yml

@@ -23,17 +23,14 @@ galaxy_info:
   platforms:
   - name: Debian
     versions:
-    - stretch
+    - buster
   - name: Ubuntu
     versions:
-    - xenial
-    - bionic
+      - bionic
+      - focal
   - name: EL
     versions:
-    - 7
-  - name: opensuse
-    versions:
-    - 15
+      - 8
   # Below are all categories currently available. Just as with
   # the platforms above, uncomment those that apply to your role.
   galaxy_tags:

vars/suse.yml

@@ -1,30 +0,0 @@
----
-# Copyright 2017, Red Hat, Inc.
-# 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.
-
-magnum_distro_packages: []
-
-# Packages for buildind the python wheels
-magnum_devel_distro_packages:
-  - python-devel
-  - libopenssl-devel
-  - libxml2-devel
-  - libxslt-devel
-  - postgresql-devel
-  - git-core
-  - libffi-devel
-  - gettext
-  - gcc
-  - systemd-devel