Bug 1284853 - Skip creating a user in the client_credentials fixture

Since Hawk credentials can now be created without an owner, there's no
need for this fixture to create a user to be associated with the test
Hawk credentials, since none of the tests using the `client_credentials`
fixture actually use the created user.

The `transactional_db` fixture is now required since it's no longer
inherited from the `test_user` fixture.

Also switch back to `.create()` rather than `.get_or_create()` now that
bug 1133273 is fixed.

tests/conftest.py

@@ -467,15 +467,12 @@ def test_sheriff(request, transactional_db):
 
 
 @pytest.fixture
-def client_credentials(request, test_user):
-    from django.conf import settings
+def client_credentials(request, transactional_db):
     from treeherder.credentials.models import Credentials
 
-    # We need to get_or_create here because of bug 1133273.
-    # It can be a straight create once that bug is solved.
-    client_credentials, _ = Credentials.objects.get_or_create(
-        client_id=settings.ETL_CLIENT_ID,
-        defaults={'owner': test_user, 'authorized': True}
+    client_credentials = Credentials.objects.create(
+        client_id='test_client',
+        authorized=True
     )
 
     def fin():

treeherder/config/settings.py

@@ -546,9 +546,6 @@ SWAGGER_SETTINGS = {"enabled_methods": ['get', ]}
 
 HAWK_CREDENTIALS_LOOKUP = 'treeherder.webapp.api.auth.hawk_lookup'
 
-# This is the client ID used by the internal data ingestion service.
-ETL_CLIENT_ID = 'treeherder-etl'
-
 # Configuration for elasticsearch backend
 ELASTIC_SEARCH = {
     "url": env.str('ELASTICSEARCH_URL', default=""),