Added tempest user for tempest container

* Currently on using tempest container, everything is running as a
  root user under the container. All the test data when copied from
  container to host, have different permission. In order to consume
  those data we need to change permission. Adding tempest user to
  tempest container fix the issue.

* New user can pass --user 'tempest' with docker run to consume it.

* It does not affect the workflow of tempest container used in tripleo ci.
Change-Id: I719b7b13197bcb1ace607f10448d76ccb1d8cdf7

docker/tempest/Dockerfile.j2

@@ -5,6 +5,8 @@ LABEL maintainer="{{ maintainer }}" name="{{ image_name }}" build-date="{{ build
 
 {% import "macros.j2" as macros with context %}
 
+{{ macros.configure_user(name='tempest') }}
+
 {% if install_type == 'binary' %}
     {% if base_distro in ['centos', 'oraclelinux', 'rhel'] %}
         {% set tempest_packages = ['openstack-tempest-all'] %}
@@ -52,3 +54,5 @@ RUN chmod 755 /usr/local/bin/kolla_extend_start
 
 {% block tempest_footer %}{% endblock %}
 {% block footer %}{% endblock %}
+
+USER tempest

kolla/common/config.py

@@ -1112,6 +1112,10 @@ USERS = {
     'storm-user': {
         'uid': 42479,
         'gid': 42479,
+    },
+    'tempest-user': {
+        'uid': 42480,
+        'gid': 42480,
     }
 }