Fix notify discovery setup (#68451)

* Fix notify discovery setup

* add test

* unsubscribe at reset

* Add guard

* move dispatcher to reload module

* only unsubscribe if platform was setup

* initialize dispatcher once and tests

* test get_service too

* add tests

* fix test

* use get_service for test invalid platform

* Test built-in reload method

* set to None after clearing dispatcher - tests

* Pathing services file

* Update tests/components/notify/test_init.py

Co-authored-by: Martin Hjelmare <marhje52@gmail.com>

* dispatcher is not set twice if integration loaded

* empty discovery payload

* Removed not needed services.yaml mock

* Update tests/components/notify/test_init.py

Co-authored-by: Martin Hjelmare <marhje52@gmail.com>

* flake8

Co-authored-by: Martin Hjelmare <marhje52@gmail.com>

homeassistant/helpers/reload.py

@@ -21,6 +21,8 @@ from .typing import ConfigType
 
 _LOGGER = logging.getLogger(__name__)
 
+PLATFORM_RESET_LOCK = "lock_async_reset_platform_{}"
+
 
 async def async_reload_integration_platforms(
     hass: HomeAssistant, integration_name: str, integration_platforms: Iterable[str]
@@ -79,8 +81,11 @@ async def _resetup_platform(
     if hasattr(component, "async_reset_platform"):
         # If the integration has its own way to reset
         # use this method.
-        await component.async_reset_platform(hass, integration_name)
-        await component.async_setup(hass, root_config)
+        async with hass.data.setdefault(
+            PLATFORM_RESET_LOCK.format(integration_platform), asyncio.Lock()
+        ):
+            await component.async_reset_platform(hass, integration_name)
+            await component.async_setup(hass, root_config)
         return
 
     # If it's an entity platform, we use the entity_platform