Use parameters in config file for trust test

``create_ctx_from_trust`` creates a context using project_id
and user_id that are set to blazar configuration file, but
the test is fixed to use "admin", which can cause unpredictable
unit test error on developer's local environment.

This patch fixes the problem.

Change-Id: Ied2451d8821dc0ac3f59fe838efec01453839909
Closes-Bug: #1777399

blazar/tests/utils/test_trusts.py

@@ -15,12 +15,17 @@
 
 import mock
 
+from oslo_config import cfg
+from oslo_config import fixture as conf_fixture
+
 from blazar import context
 from blazar import tests
 from blazar.utils.openstack import base
 from blazar.utils.openstack import keystone
 from blazar.utils import trusts
 
+CONF = cfg.CONF
+
 
 class TestTrusts(tests.TestCase):
     def setUp(self):
@@ -34,6 +39,8 @@ class TestTrusts(tests.TestCase):
         self.patch(self.context, 'current')
         self.patch(self.base, 'url_for').return_value = 'http://www.foo.fake'
 
+        self.cfg = self.useFixture(conf_fixture.Config(CONF))
+
     def test_create_trust(self):
         correct_trust = self.client().trusts.create()
 
@@ -49,6 +56,8 @@ class TestTrusts(tests.TestCase):
         self.client.assert_called_once_with(trust_id='1')
 
     def test_create_ctx_from_trust(self):
+        self.cfg.config(os_admin_project_name='admin')
+        self.cfg.config(os_admin_username='admin')
         fake_item = self.client().service_catalog.catalog.__getitem__()
         fake_ctx_dict = {'_BaseContext__values': {
             'auth_token': self.client().auth_token,