Test idempotence of deploy and teardown in CI

Not currently checking for zero changed tasks (this would fail), but
checking we can at least run the playbooks a second time.

Change-Id: I045f9b0c222f2f35521319b3dc17c269f070e0dc

playbooks/tenks-deploy-teardown/run.yml

@@ -27,6 +27,15 @@
           ansible/deploy.yml > {{ logs_dir }}/ansible/tenks-deploy
         chdir: "{{ tenks_src_dir }}"
 
+    - name: Test idempotence of deploy
+      shell:
+        cmd: >-
+          {{ ansible_playbook_bin }} -vvv
+          --inventory ansible/inventory
+          --extra-vars=@{{ tenks_overrides_path }}
+          ansible/deploy.yml > {{ logs_dir }}/ansible/tenks-deploy-idempotence
+        chdir: "{{ tenks_src_dir }}"
+
     - name: Get some diagnostic info for the tenks cluster
       include_role:
         name: tenks-diagnostics
@@ -42,3 +51,12 @@
           --extra-vars=@{{ tenks_overrides_path }}
           ansible/teardown.yml > {{ logs_dir }}/ansible/tenks-teardown
         chdir: "{{ tenks_src_dir }}"
+
+    - name: Test idempotence of teardown
+      shell:
+        cmd: >-
+          {{ ansible_playbook_bin }} -vvv
+          --inventory ansible/inventory
+          --extra-vars=@{{ tenks_overrides_path }}
+          ansible/teardown.yml > {{ logs_dir }}/ansible/tenks-teardown-idempotence
+        chdir: "{{ tenks_src_dir }}"