Fix with_* loop for ansible 2.9

Ansible changed handling loop variables in 2.9 [0]. Use explicit
loop statements instead of with_*.

[0] https://docs.ansible.com/ansible/latest/user_guide/playbooks_loops.html#migrating-to-loop

Change-Id: Ic063adbb672c3ff6bb4cca346d689630a7a37f34

roles/stage-output/tasks/main.yaml

@@ -1,7 +1,7 @@
 - name: Register sources
   stat:
     path: "{{ zj_source.key }}"
-  with_dict: "{{ zuul_copy_output }}"
+  loop: "{{ zuul_copy_output|dict2items }}"
   loop_control:
     loop_var: zj_source
   register: sources