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: Ia0b927fe775d5638cd09ecb91af550892764353d

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/ceilometer_install.yml

@@ -29,7 +29,7 @@
   package:
     name: "{{ ceilometer_package_list }}"
     state: "{{ ceilometer_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/suse.yml

@@ -1,46 +0,0 @@
----
-# Copyright 2014, Rackspace US, 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.
-
-ceilometer_distro_packages:
-  - git-core
-  - python2-libvirt-python
-  - python3-libvirt-python
-
-ceilometer_devel_distro_packages:
-  - pkg-config
-  - systemd-devel
-  - which
-  - libvirt-devel
-  - libxml2-devel
-  - libxslt-devel
-
-ceilometer_service_distro_packages:
-  - openstack-ceilometer
-  - openstack-ceilometer-agent-central
-  - openstack-ceilometer-agent-compute
-  - openstack-ceilometer-agent-ipmi
-  - openstack-ceilometer-agent-notification
-  - openstack-ceilometer-polling
-  - python-systemd
-
-ceilometer_oslomsg_amqp1_distro_packages:
-  - cyrus-sasl
-  - cyrus-sasl-plain
-  - cyrus-sasl-digestmd5
-
-ceilometer_packages_to_symlink:
-  - python2-libvirt-python
-  - python3-libvirt-python