Don't attempt to loop over undefined variables

Ansible-core 2.19 has changed evaluation order, so delegate_to is now
processed before the condition, so delegate
target should be resolvable right away.

Thus, we replace condition with a default value, which also will result
in a skipped task.

Change-Id: Iaa93f72784f83deac386adb60dbd999cf5571837
Signed-off-by: Dmitriy Rabotyagov <dmitriy.rabotyagov@cleura.com>

tasks/keystone_credential_create.yml

@@ -46,9 +46,8 @@
   ansible.builtin.slurp:
     src: "{{ item.file }}"
   delegate_to: "{{ item.host }}"
-  with_items: "{{ existing_credential_keys }}"
+  with_items: "{{ existing_credential_keys | default([]) }}"
   register: collected_existing_credential_keys
-  when: existing_credential_keys is defined
 
 - name: Ensure the target directory exists on the master Keystone container
   ansible.builtin.file: