update: fix a typo

`hostvars[groups[mon_host]]['ansible_hostname']` seems to be a typo.
That should be `hostvars[mon_host]['ansible_hostname']`

Signed-off-by: Guillaume Abrioux <gabrioux@redhat.com>
(cherry picked from commit 7c99b6df6d)

infrastructure-playbooks/rolling_update.yml

@@ -188,7 +188,7 @@
         caps:
           mon: "allow profile {{ item.0 }}"
         cluster: "{{ cluster }}"
-        containerized: "{{ 'docker exec ceph-mon-' + hostvars[groups[mon_host]]['ansible_hostname'] if containerized_deployment else None }}"
+        containerized: "{{ 'docker exec ceph-mon-' + hostvars[mon_host]['ansible_hostname'] if containerized_deployment else None }}"
       when:
         - cephx
       delegate_to: "{{ mon_host }}"