Ensure timezone tests reset system timezone to original value (#39326)

(cherry picked from commit fda67bae50)

test/integration/targets/timezone/tasks/main.yml

@@ -1,15 +1,21 @@
-- name: set timezone to Etc/UTC
+- name: Set timezone to Etc/UTC
   timezone:
     name: Etc/UTC
+  register: original_timezone
 
-- name: set timezone to Australia/Brisbane
+- block:
+    - name: Set timezone to Australia/Brisbane
       timezone:
         name: Australia/Brisbane
       register: timezone_set
 
-- name: ensure timezone changed
+    - name: Ensure timezone changed
       assert:
         that:
-      - timezone_set.changed
+          - timezone_set is changed
           - timezone_set.diff.after.name == 'Australia/Brisbane'
           - timezone_set.diff.before.name == 'Etc/UTC'
+  always:
+    - name: Restore original system timezone - {{ original_timezone.diff.before.name }}
+      timezone:
+        name: "{{ original_timezone.diff.before.name }}"