CI: Add work dir

It's useful to have a templated out version of the Dockerfiles
in order to diagnose errors like "error on line xxx" after
tests/templates/template-override.j2 gets applied.

Change-Id: I5443454d8b020aa1c5552e11f6039e582a002431

tests/playbooks/run.yml

@@ -8,6 +8,7 @@
       DEFAULT:
         debug: true
         logs_dir: "{{ kolla_build_logs_dir }}"
+        work_dir: "{{ kolla_logs_dir }}/work_dir"
         quiet: true
         base: "{{ base_distro }}"
         template_override: /etc/kolla/template_overrides.j2