hostkey-provider: implement fallback if fqdn fact is not available

hostkey-provider/templates/known_hosts.j2

@@ -5,10 +5,11 @@
 {{ v['ansible_host'] }},{{ v['ansible_all_ipv4_addresses']|join(',') }},{{ v['ansible_all_ipv6_addresses']|join(',') }} ssh-rsa {{ v['ansible_ssh_host_key_rsa_public'] }}
 {%- else -%}
 #}
-{%- if 'ansible_local' in hostvars[hostkeys_collector] and 'hostkeys_' ~ v['ansible_fqdn'] in hostvars[hostkeys_collector]['ansible_local'] %}
-{%- set c = hostvars[hostkeys_collector]['ansible_local']['hostkeys_'~ v['ansible_fqdn']]['collected'] -%}
-{{ v['ansible_fqdn'] }},{{ c['ipv4'] }},{{ c['ipv6'] }} ssh-ed25519 {{ c['ed25519'] }}
-{{ v['ansible_fqdn'] }},{{ c['ipv4'] }},{{ c['ipv6'] }} ssh-rsa {{ c['rsa'] }}
+{%- set fqdn = v['ansible_fqdn'] if 'ansible_fqdn' in v else v['ansible_host'] -%}
+{%- if 'ansible_local' in hostvars[hostkeys_collector] and 'hostkeys_' ~ fqdn in hostvars[hostkeys_collector]['ansible_local'] %}
+{%- set c = hostvars[hostkeys_collector]['ansible_local']['hostkeys_'~ fqdn]['collected'] -%}
+{{ fqdn }},{{ c['ipv4'] }},{{ c['ipv6'] }} ssh-ed25519 {{ c['ed25519'] }}
+{{ fqdn }},{{ c['ipv4'] }},{{ c['ipv6'] }} ssh-rsa {{ c['rsa'] }}
 {% endif -%}
 {#
 {%- endif -%}