[download] Don't fail on 304 Not Modified (#10452)

i.e when file was not modified since last download

roles/download/tasks/download_file.yml

@@ -101,7 +101,9 @@
     run_once: "{{ download_force_cache }}"
     register: get_url_result
     become: "{{ not download_localhost }}"
-    until: "'OK' in get_url_result.msg or 'file already exists' in get_url_result.msg"
+    until: "'OK' in get_url_result.msg or
+      'file already exists' in get_url_result.msg or
+      get_url_result.status_code == 304"
     retries: "{{ download_retries }}"
     delay: "{{ retry_stagger | default(5) }}"
     environment: "{{ proxy_env }}"