postgresql: Cast sorted_old_postgres_pods as list

With ansible 2.9.27 (operator-sdk v1.27.0) then the reverse filter
returns an iterator so we need to cast it to list.
The behavior doesn't exist when using a more recent operator-sdk
version like v1.34.0 (ansible-core 2.15.8) but using the list
filter on that version works too (even if not needed)

"sorted_old_postgres_pods": "<list_reverseiterator object at 0x7f539eaa5610>"

Signed-off-by: Dimitri Savineau <dsavinea@redhat.com>

roles/installer/tasks/database_configuration.yml

@@ -129,7 +129,7 @@
       set_fact:
         sorted_old_postgres_pods: "{{ filtered_old_postgres_pods |
           sort(attribute='metadata.name') |
-          reverse }}"
+          reverse | list }}"
       when: filtered_old_postgres_pods | length