CI: store only templated out Dockerfiles in work_dir

Change-Id: I0832d7997536f5f0dc195d5038545b6cc220f0fa
(cherry picked from commit c45a742)

Author: mnasiadka

tests/playbooks/run.yml

@@ -42,5 +42,8 @@
         src: "{{ zuul.executor.work_root }}/{{ zuul.project.src_dir }}/tests/templates/template_overrides.j2"
         dest: /etc/kolla/template_overrides.j2
 
+    - name: Run kolla-build to template out dockerfiles
+      command: "{{ virtualenv_path }}/bin/kolla-build --template-only --work-dir {{ kolla_build_logs_dir }}/work_dir"
+
     - name: Run kolla-build
       command: "{{ virtualenv_path }}/bin/kolla-build"