Enable logging for tempest container

* In order to make sure tempest container is available in CI,
  It adds the logging for the same in /var/log/containers/tempest.

Change-Id: I3d526b374b6233bad69f5c6be12036b3ede37028

docker/services/tempest.yaml

@@ -46,7 +46,29 @@ outputs:
       # available on undercloud.
       service_name: tempest
       docker_config:
-        volumes: ''
+        step_2:
+          tempest_init_logs:
+            image: &tempest_image {get_param: DockerTempestImage}
+            privileged: false
+            user: root
+            volumes:
+              - /var/log/containers/tempest:/var/log/tempest
+            command: ['/bin/bash', '-c', 'chown -R tempest:tempest /var/log/tempest']
+      host_prep_tasks:
+        - name: create persistent logs directory
+          file:
+            path: "{{ item }}"
+            state: directory
+          with_items:
+            - /var/log/containers/tempest
+            - /var/log/tempest
+        - name: Tempest logs readme
+          copy:
+            dest: /var/log/tempest/readme.txt
+            content: |
+              Log files from tempest containers can be found under
+              /var/log/containers/tempest.
+          ignore_errors: true
       puppet_config:
         config_volume: ''
         step_config: ''