test: switch default test store to the split store

It's long past time that the default test modulestore was Split,
instead of Old Mongo. This commit switches the default store and
fixes some tests that now fail:
- Tests that didn't expect MFE to be enabled (because we don't
  enable MFE for Old Mongo) - opt out of MFE for those
- Tests that hardcoded old key string formats
- Lots of other random little differences

In many places, I didn't spend much time trying to figure out how to
properly fix the test, and instead just set the modulestore to Old
Mongo.

For those tests that I didn't spend time investigating, I've set
the modulestore to TEST_DATA_MONGO_AMNESTY_MODULESTORE - search for
that string to find further work.

lms/djangoapps/program_enrollments/api/tests/test_linking.py

@@ -10,6 +10,7 @@ from django.test import TestCase
 from edx_django_utils.cache import RequestCache
 from opaque_keys.edx.keys import CourseKey
 from testfixtures import LogCapture
+from xmodule.modulestore.tests.django_utils import ModuleStoreTestCase
 
 from common.djangoapps.student.api import get_course_access_role
 from common.djangoapps.student.roles import CourseStaffRole
@@ -363,7 +364,7 @@ class TestLinkProgramEnrollments(TestLinkProgramEnrollmentsMixin, TestCase):
         self._assert_user_enrolled_in_program_courses(self.user_2, self.program, self.fruit_course, self.animal_course)
 
 
-class TestLinkProgramEnrollmentsErrors(TestLinkProgramEnrollmentsMixin, TestCase):
+class TestLinkProgramEnrollmentsErrors(TestLinkProgramEnrollmentsMixin, ModuleStoreTestCase):
     """ Tests for linking error behavior """
 
     def test_program_enrollment_not_found__nonexistant(self):

lms/djangoapps/program_enrollments/rest_api/v1/tests/test_views.py

@@ -20,6 +20,9 @@ from organizations.tests.factories import OrganizationFactory as LMSOrganization
 from rest_framework import status
 from rest_framework.test import APITestCase
 from social_django.models import UserSocialAuth
+from xmodule.modulestore.tests.django_utils import TEST_DATA_MONGO_AMNESTY_MODULESTORE, SharedModuleStoreTestCase
+from xmodule.modulestore.tests.factories import CourseFactory as ModulestoreCourseFactory
+from xmodule.modulestore.tests.factories import ItemFactory
 
 from common.djangoapps.course_modes.models import CourseMode
 from common.djangoapps.student.models import CourseEnrollment
@@ -52,9 +55,6 @@ from openedx.core.djangoapps.catalog.tests.factories import (
 from openedx.core.djangoapps.content.course_overviews.models import CourseOverview
 from openedx.core.djangoapps.content.course_overviews.tests.factories import CourseOverviewFactory
 from openedx.core.djangolib.testing.utils import CacheIsolationMixin
-from xmodule.modulestore.tests.django_utils import SharedModuleStoreTestCase  # lint-amnesty, pylint: disable=wrong-import-order
-from xmodule.modulestore.tests.factories import CourseFactory as ModulestoreCourseFactory  # lint-amnesty, pylint: disable=wrong-import-order
-from xmodule.modulestore.tests.factories import ItemFactory  # lint-amnesty, pylint: disable=wrong-import-order
 
 from .. import views
 from ..constants import (
@@ -96,6 +96,7 @@ class EnrollmentsDataMixin(ProgramCacheMixin):
     Mixin to define some shared test data objects for program/course enrollment
     view tests.
     """
+    MODULESTORE = TEST_DATA_MONGO_AMNESTY_MODULESTORE
     view_name = 'SET-ME-IN-SUBCLASS'
 
     @classmethod
@@ -1636,6 +1637,8 @@ class ProgramCourseEnrollmentOverviewGetTests(
     """
     Tests for the ProgramCourseEnrollmentOverview view GET method.
     """
+    MODULESTORE = TEST_DATA_MONGO_AMNESTY_MODULESTORE
+
     patch_resume_url = mock.patch(
         _UTILS_PATCH_FORMAT.format('get_resume_urls_for_enrollments'),
         autospec=True,