Make create_user domain-aware for V3CredsClient

Currently create_user is just inherited from CredsClient and, therefore,
does not pass a domain_id to the /v3/users POST API call to create a new
user. As a result a domain with id "default" is used as no domain is
explicitly passed in the API call which results in 404 NOT FOUND and the
following error: "Could not find domain: default.".

The right way is passing a domain from:

1) CONF.auth.admin_domain_name
2) CONF.auth.default_credentials_domain_name

This is already taken into account when a domain_name is passed from
identity_utils during object instantiation and used for in the
create_project method specific to V3CredsClient. The API calls only
accept a domain_id which is why creds_domain field of a V3CredsClient
object is used to store an id of a domain_name domain passed via
constructor. The same can be used for create_user method specific to v3.

Change-Id: I66f22c61d7a8596cafdc415654edfecdc5495d2e
Closes-Bug: #1613819

releasenotes/notes/make-create-user-domain-aware-for-v3-creds-client-5054f58e715adc0c.yaml

@@ -0,0 +1,9 @@
+---
+fixes:
+  - |
+    [`bug 1613819 <https://bugs.launchpad.net/tempest/+bug/1613819>`_]
+    admin_domain_name and default_credentials_domain_name parameters
+    under [auth] now affect a domain used for creating test users just
+    as they affect it for projects. Previously a domain with an id set
+    to "default" had to be present in order for test user creation to
+    succeed with Keystone v3.

tempest/lib/common/cred_client.py

@@ -173,6 +173,22 @@ class V3CredsClient(CredsClient):
         self.domains_client.update_domain(domain_id, enabled=False)
         self.domains_client.delete_domain(domain_id)
 
+    def create_user(self, username, password, project=None, email=None,
+                    domain_id=None):
+        params = {'name': username,
+                  'password': password,
+                  'domain_id': domain_id or self.creds_domain['id']}
+        # with keystone v3, a default project is not required
+        if project:
+            params[self.project_id_param] = project['id']
+        # email is not a first-class attribute of a user
+        if email:
+            params['email'] = email
+        user = self.users_client.create_user(**params)
+        if 'user' in user:
+            user = user['user']
+        return user
+
     def get_credentials(
             self, user, project, password, domain=None, system=None):
         # User, project and domain already include both ID and name here,

tempest/tests/lib/common/test_cred_client.py

@@ -111,3 +111,21 @@ class TestCredClientV3(base.TestCase):
         self.assertIsNone(ret.project_name)
         self.assertEqual(ret.system, {'system': 'all'})
         self.assertEqual(ret.domain_name, 'some_domain')
+
+    def test_create_user(self):
+        self.users_client.create_user.return_value = {
+            'user': 'a_user'
+        }
+        fake_project = {
+            'id': 'fake_project_id',
+        }
+        res = self.creds_client.create_user('fake_username',
+                                            'fake_password',
+                                            fake_project,
+                                            'fake_email')
+        self.assertEqual('a_user', res)
+        self.users_client.create_user.assert_called_once_with(
+            name='fake_username', password='fake_password',
+            project_id=fake_project['id'],
+            email='fake_email',
+            domain_id='fake_domain_id')