Fix validation runs in a containerized environment

This fix addresses the following issues:
- No validations user present in the mistral-executor container
- The ssh_keys environment isn't initially created

Change-Id: I53078723b0995d6cd9590f119b28a7ca2b95dafd
Closes-Bug: #1789886

container-images/tripleo_kolla_template_overrides.j2

@@ -376,6 +376,9 @@ RUN mkdir -p /openstack && \
 RUN mkdir -p /openstack && \
     ln -s /usr/share/openstack-tripleo-common/healthcheck/mistral-executor /openstack/healthcheck && \
     chmod a+rx /openstack/healthcheck
+USER root
+RUN useradd validations
+USER mistral
 {% endblock %}
 
 {% block mistral_event_engine_footer %}

tripleo_common/actions/validations.py

@@ -131,8 +131,19 @@ class RunValidationAction(base.TripleOAction):
         swift = self.get_object_client(context)
 
         identity_file = None
+
+        # Make sure the ssh_keys environment exists
         try:
             env = mc.environments.get('ssh_keys')
+        except Exception:
+            workflow_env = {
+                'name': 'ssh_keys',
+                'description': 'SSH keys for TripleO validations',
+                'variables': password_utils.create_ssh_keypair()
+            }
+            env = mc.environments.create(**workflow_env)
+
+        try:
             private_key = env.variables['private_key']
             identity_file = utils.write_identity_file(private_key)