arm64 mirror : update to Focal

We have having constant issues with the bionic arm64 mirror shutting
itself off.  Before we go too far down the path of debugging what
appears to be a kernel oops issue, let's rebuild it as focal.

Update the sources list in the base.  Update the testing to use a
focal node.

Change-Id: I5b7106e2263010ff353e8a1de43e73b0c0ec57e1

playbooks/roles/base/repos/files/sources.list.focal.aarch64

@@ -0,0 +1,8 @@
+# This file is kept updated by ansible, adapted from
+# https://help.ubuntu.com/lts/serverguide/configuration.html
+# Note the use of ports.ubuntu.com.
+
+deb http://ports.ubuntu.com/ubuntu-ports/ focal main universe
+deb http://ports.ubuntu.com/ubuntu-ports/ focal-updates main universe
+deb http://ports.ubuntu.com/ubuntu-ports/ focal-backports main universe
+deb http://ports.ubuntu.com/ubuntu-ports/ focal-security main universe

zuul.d/system-config-run.yaml

@@ -371,6 +371,7 @@
     files:
       - playbooks/install-ansible.yaml
       - roles/
+      - playbooks/roles/base/
       - inventory/service/group_vars/mirror.yaml
       - playbooks/roles/mirror/
       - playbooks/roles/letsencrypt
@@ -401,7 +402,7 @@
         - name: bridge.openstack.org
           label: ubuntu-bionic-arm64
         - name: mirror01.openafs.provider.opendev.org
-          label: ubuntu-bionic-arm64
+          label: ubuntu-focal-arm64
 
 - job:
     name: system-config-run-mirror-update