Move ara output generation to post playbook

When there are issues, we hit POST FAILURE because ara generate gets
skipped. Move it.

Change-Id: Ib54f78c548999ed330d44e77ecbfc90944fec459
diff --git a/.zuul.yaml b/.zuul.yaml
index 1912eb5..26e4650 100644
--- a/.zuul.yaml
+++ b/.zuul.yaml
@@ -19,7 +19,9 @@
     nodes: zuul-functional
     pre-run: playbooks/zuul-stream/pre
     run: playbooks/zuul-stream/functional
-    post-run: playbooks/zuul-stream/post
+    post-run:
+      - playbooks/zuul-stream/post
+      - playbooks/zuul-stream/post-ara
     required-projects:
       - openstack/ara