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: I55037805e59cb6d727593f467e98568a4c030e74

meta/main.yml

@@ -20,16 +20,16 @@ galaxy_info:
   license: Apache2
   min_ansible_version: 2.0
   platforms:
+    - name: Debian
+      versions:
+        - buster
     - name: Ubuntu
       versions:
-        - xenial
         - bionic
+        - focal
     - name: EL
       versions:
-        - 7
+        - 8
-    - name: opensuse
-      versions:
-        - 15
   categories:
     - systemd
     - development

tasks/systemd_install.yml

@@ -35,7 +35,7 @@
     - name: Install the EPEL repository
       yum_repository:
         name: epel-systemd_mounts
-        baseurl: "{{ systemd_centos_epel_mirror ~ '/' ~ ansible_facts['distribution_major_version'] ~ (ansible_facts['distribution_major_version'] is version('8', '>=')) | ternary('/Everything/', '/') ~ ansible_facts['architecture'] }}"
+        baseurl: "{{ systemd_centos_epel_mirror ~ '/' ~ ansible_facts['distribution_major_version'] ~ '/Everything/' ~ ansible_facts['architecture'] }}"
         description: "Extra Packages for Enterprise Linux {{ ansible_facts['distribution_major_version'] }} - $basearch"
         gpgcheck: yes
         enabled: yes

tests/test-create-nfs-dev.yml

@@ -81,4 +81,3 @@
       ubuntu: "nfs-kernel-server"
       debian: "nfs-kernel-server"
       centos: "nfs-utils"
-      opensuse: "nfs-kernel-server"