Fix credential existence check for rgw usage exporter

credential_check.stdout is a string representation of a list, and as such will never return true when compared to an empty Python list.

Passing credential_check.stdout through the from_json filter casts the string to a list, and the equality can be properly evaluated.

Author: m-bull

etc/kayobe/ansible/deploy-radosgw-usage-exporter.yml

@@ -66,7 +66,7 @@
           vars:
             ansible_host: "{{ hostvars[groups['controllers'][0]].ansible_host }}"
           run_once: true
-          when: credential_check.stdout == []
+          when: credential_check.stdout | from_json == []
 
         - name: Query ec2 credential for ceph_rgw
           ansible.builtin.command: >