Fix leaky tests

arkindex/dataimport/tests/test_imports.py

arkindex/dataimport/tests/test_templates.py

arkindex/dataimport/tests/test_utils.py

arkindex/dataimport/tests/test_workeractivity.py

arkindex/dataimport/tests/test_workers.py

arkindex/documents/tests/test_bulk_elements.py

arkindex/documents/tests/test_corpus.py

arkindex/documents/tests/test_create_transcriptions.py

arkindex/documents/tests/test_edit_transcriptions.py

arkindex/documents/tests/test_manifest.py

arkindex/documents/tests/test_parents_elements.py

arkindex/images/tests/test_image_api.py

arkindex/images/tests/test_perform_check.py

arkindex/images/tests/test_thumbnail.py

arkindex/project/tests/__init__.py

arkindex/project/tests/test_arrayfield.py

arkindex/users/tests/test_generic_memberships.py

arkindex/users/tests/test_jobs.py