🐛 Init webui only once in tests

[huchenlei]

In most recent version of A1111. module.initialize.initialize is only expected to be called once. Calling it multiple times gives following error:

ERROR extensions/sd-webui-controlnet/tests/annotator_tests/openpose_tests/detection_test.py - RuntimeError: patch for register_schedule is already applied
ERROR extensions/sd-webui-controlnet/tests/annotator_tests/openpose_tests/json_encode_test.py - RuntimeError: patch for register_schedule is already applied
ERROR extensions/sd-webui-controlnet/tests/annotator_tests/openpose_tests/openpose_e2e_test.py - RuntimeError: patch for register_schedule is already applied
ERROR extensions/sd-webui-controlnet/tests/cn_script/batch_hijack_test.py - RuntimeError: patch for register_schedule is already applied
ERROR extensions/sd-webui-controlnet/tests/cn_script/cn_script_test.py - RuntimeError: patch for register_schedule is already applied
ERROR extensions/sd-webui-controlnet/tests/cn_script/utils_test.py - RuntimeError: patch for register_schedule is already applied
ERROR extensions/sd-webui-controlnet/tests/external_code_api/external_code_test.py - RuntimeError: patch for register_schedule is already applied
ERROR extensions/sd-webui-controlnet/tests/external_code_api/importlib_reload_test.py - RuntimeError: patch for register_schedule is already applied
ERROR extensions/sd-webui-controlnet/tests/external_code_api/script_args_test.py - RuntimeError: patch for register_schedule is already applied
ERROR extensions/sd-webui-controlnet/tests/web_api/control_types_test.py - RuntimeError: patch for register_schedule is already applied
ERROR extensions/sd-webui-controlnet/tests/web_api/detect_test.py - RuntimeError: patch for register_schedule is already applied
ERROR extensions/sd-webui-controlnet/tests/web_api/img2img_test.py - RuntimeError: patch for register_schedule is already applied
ERROR extensions/sd-webui-controlnet/tests/web_api/txt2img_test.py - RuntimeError: patch for register_schedule is already applied

This PR makes sure that we only call initialize once in CI tests.