Adds ceph-systemd tag in external_upgrade_tasks for systemd units

When upgrading the host operating system we'll also replace docker
with podman; ceph-ansible provides for a special playbook meant
to refresh the systemd units to work with podman.

This change adds a task which on upgrade will execute the special
playbook. It requires ceph_ansible_limit to be set by the user as
that gets translated into a --limit option for the playbook execution
so that it runs only against a specific node undergoing upgrade
of the host operating system.

Change-Id: I99bc5342360e307a9ee499cde5f2a0b5d78170f8
(cherry picked from commit e8048707f7)
(cherry picked from commit e866739b6c)

deployment/ceph-ansible/ceph-base.yaml

@@ -710,6 +710,7 @@ outputs:
                     - '{{playbook_dir}}/ceph-ansible/inventory.yml'
                     - '--extra-vars'
                     - '@{{playbook_dir}}/ceph-ansible/extra_vars.yml'
+                    - '{% if ceph_ansible_limit is defined and ceph_ansible_limit|length > 0 %}--limit {{ ceph_ansible_limit }}{% endif %}'
             - name: run ceph-ansible (immediate log at {{playbook_dir}}/ceph-ansible/ceph_ansible_command.log)
               # needs become to be able to read the ssh private key
               become: true
@@ -784,6 +785,16 @@ outputs:
               set_fact:
                 ceph_ansible_playbooks_default: ["/usr/share/ceph-ansible/infrastructure-playbooks/rolling_update.yml"]
       external_upgrade_tasks:
+        - when: step|int == 0
+          tags: ceph-systemd
+          block:
+            - name: stop if _limit is unset
+              fail:
+                msg: The ceph-ansible systemd units migration playbook limit is not set; please use -e ceph_ansible_limit=##nodename##
+              when: (ceph_ansible_limit is not defined) or (ceph_ansible_limit|length == 0)
+            - name: set ceph_ansible_playbooks_default
+              set_fact:
+                ceph_ansible_playbooks_default: ["/usr/share/ceph-ansible/infrastructure-playbooks/docker-to-podman.yml"]
         - when: step|int == 0
           tags: ceph
           block: