ensure-podman: Remove kubic from Ubuntu 18.04 and drop 20.04

The kubic repo no longer has packages for Ubuntu 18.04.  Use the
PPA instead.

Kubic also dropped packages for 20.04, but the PPA is not available.
Since we have no source for podman packages on 20.04, drop support.

Change-Id: I0fa441cd2fe4ec35c1bbe6630324965e223d7512

roles/ensure-podman/tasks/Ubuntu-18.04.yaml

@@ -1,15 +1,4 @@
-- name: Add kubic project repository
-  when: ansible_architecture == "x86_64"
-  include_role:
-    name: ensure-package-repositories
-  vars:
-    repositories_keys:
-      - url: "https://download.opensuse.org/repositories/devel:/kubic:/libcontainers:/stable/xUbuntu_{{ ansible_distribution_version }}/Release.key"
-    repositories_list:
-      - repo: "deb https://download.opensuse.org/repositories/devel:/kubic:/libcontainers:/stable/xUbuntu_{{ ansible_distribution_version }}/ /"
-
 - name: Add project atomic PPA repository
-  when: ansible_architecture != "x86_64"
   include_role:
     name: ensure-package-repositories
   vars:

roles/ensure-podman/tasks/Ubuntu-20.04.yaml

@@ -0,0 +1,3 @@
+- name: Not supported
+  fail:
+    msg: Ubuntu 20.04 not supported due to no known source of podman packages.

zuul-tests.d/container-roles-jobs.yaml

@@ -396,15 +396,6 @@
         - name: ubuntu-bionic
           label: ubuntu-bionic
 
-- job:
-    name: zuul-jobs-test-ensure-podman-ubuntu-focal
-    description: Tests ensure-podman role on ubuntu-focal
-    parent: zuul-jobs-test-ensure-podman
-    nodeset:
-      nodes:
-        - name: ubuntu-focal
-          label: ubuntu-focal
-
 - job:
     name: zuul-jobs-test-ensure-podman-debian-bullseye
     description: Tests ensure-podman role on debian-bullseye
@@ -467,7 +458,6 @@
         - zuul-jobs-test-ensure-podman-centos-8-stream
         - zuul-jobs-test-ensure-podman-fedora-35
         - zuul-jobs-test-ensure-podman-ubuntu-bionic
-        - zuul-jobs-test-ensure-podman-ubuntu-focal
         - zuul-jobs-test-ensure-podman-debian-bullseye
         - zuul-jobs-test-ensure-skopeo-fedora-35
         - zuul-jobs-test-ensure-skopeo-ubuntu-bionic
@@ -491,7 +481,6 @@
         - zuul-jobs-test-ensure-kubernetes-crio
         - zuul-jobs-test-ensure-podman-centos-8-stream
         - zuul-jobs-test-ensure-podman-ubuntu-bionic
-        - zuul-jobs-test-ensure-podman-ubuntu-focal
         - zuul-jobs-test-ensure-podman-debian-bullseye
         - zuul-jobs-test-ensure-skopeo-fedora-35
         - zuul-jobs-test-ensure-skopeo-ubuntu-bionic