fix!: use inventory_hostname if ansible_host is unset

If using FQDNs within an ansible inventory the variable `ansible_host`
never gets set causing an error when setting `mon_ansible_host`.

Author: jackhodgkiss

roles/cephadm/tasks/osds.yml

@@ -3,7 +3,7 @@
 # correctly when setting ansible_host in the next task.
 - name: Set a fact about the Ansible host
   set_fact:
-    mon_ansible_host: "{{ hostvars[inventory_hostname].ansible_host }}"
+    mon_ansible_host: "{{ hostvars[inventory_hostname].ansible_host | default(inventory_hostname) }}"
 
 - name: Add OSDs individually
   command: