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: Ibde83024d1c3a7fc2a91ebaa14f33ad1976a7b22

defaults/main.yml

@@ -37,7 +37,7 @@ memcached_package_state: "latest"
 #
 # Setting the following variable to 'yes' will disable the PrivateDevices
 # setting in the systemd unit file for MemcacheD on CentOS 7 hosts.
-memcached_disable_privatedevices: "{{ ansible_facts['pkg_mgr'] == 'yum' }}"
+memcached_disable_privatedevices: "{{ ansible_facts['pkg_mgr'] == 'dnf' }}"
 
 # The default memcache memory setting is to use .25 of the available system ram
 # as long as that value is < 8192. However you can set the `memcached_memory`

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
     - memcached

vars/gentoo.yml

@@ -1,24 +0,0 @@
----
-# Copyright 2019, Matthew Thode
-#
-# 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.
-
-memcached_user: memcached
-
-memcached_distro_packages:
-  - net-misc/memcached
-  - net-analyzer/netcat
-
-memcached_conf_template: memcached.gentoo.j2
-
-memcached_conf_dest: /etc/memcached.conf

vars/suse.yml

@@ -1,26 +0,0 @@
----
-# 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.
-
-memcached_user: memcached
-
-memcached_distro_packages:
-  - memcached
-  - netcat-openbsd
-
-memcached_conf_template: memcached.suse.j2
-
-memcached_systemd_service: memcached.service.suse
-
-memcached_conf_dest: /etc/sysconfig/memcached