Fix prechecks group exist check

Fixes group existence assert to iterate over groups instead of group_names.

Author: darmach

changelogs/changelog.yaml

@@ -33,3 +33,8 @@ releases:
     fragments:
     - sudo-fix.yml
     release_date: '2025-01-08'
+  1.19.2:
+    changes:
+      bugfixes:
+      - prechecks - fix groups existing assertion
+    release date: '2025-10-09'

roles/cephadm/tasks/prechecks.yml

@@ -1,7 +1,7 @@
 ---
 - name: Assert that required Ansible groups exist
   ansible.builtin.assert:
-    that: "'{{ item }}' in group_names"
+    that: "'{{ item }}' in groups"
     msg: "Ansible '{{ item }}' group does not exist - please create one"
   loop:
     - ceph