Rely on the HOSTNAME var to resolve the mon container name

We previously used the {{ ansible_hostname }} variable as a replacement
for ${HOSTNAME} when the ceph-mon container name needed to be resolved
during the FFU process.
However, sounds like {{ ansible_hostname }} doesn't return the value of
the delegated host [1].
The purpose of this change is to compute the hostname relying on the
exported env var and it's supposed to fix the tls-everywhere use case
(when a more complex domain is provided).

[1] https://github.com/ansible/ansible/issues/14958

Closes-Bug: #1903537
Change-Id: I77e3e5e4336a5d3f76b10d09cf7034023fbec075
(cherry picked from commit 3e2371f71f)

deployment/ceph-ansible/ceph-osd.yaml

@@ -93,7 +93,7 @@ outputs:
                 register: check_docker_cli
                 check_mode: false
               - name: Set noout flag
-                shell: "{{ container_client }} exec -u root ceph-mon-{{ ansible_hostname }} ceph osd set {{ item }}"
+                shell: "{{ container_client }} exec -u root ceph-mon-${HOSTNAME%%.*} ceph osd set {{ item }}"
                 become: true
                 with_items:
                   - noout
@@ -120,7 +120,7 @@ outputs:
         list_concat:
         - {get_attr: [CephBase, role_data, post_upgrade_tasks]}
         - - name: Unset noout flag
-            shell: "{{ container_cli }} exec -u root ceph-mon-{{ ansible_hostname }} ceph osd unset {{ item }}"
+            shell: "{{ container_cli }} exec -u root ceph-mon-${HOSTNAME%%.*} ceph osd unset {{ item }}"
             with_items:
               - noout
               - norecover