AAP-43117 Additional dispatcher removal simplifications and waiting reaper updates (#16243)

* Additional dispatcher removal simplifications and waiting repear updates

* Fix double call and logging message

* Implement bugbot comment, should reap running on lost instances

* Add test case for new pending behavior

awx/main/dispatch/prefork.py

@@ -0,0 +1,33 @@
+import django
+
+# dispatcherd publisher logic is likely to be used, but needs manual preload
+from dispatcherd.brokers import pg_notify  # noqa
+
+# Cache may not be initialized until we are in the worker, so preload here
+from channels_redis import core  # noqa
+
+from awx import prepare_env
+
+from dispatcherd.utils import resolve_callable
+
+prepare_env()
+
+django.setup()  # noqa
+
+
+from django.conf import settings
+
+# Preload all periodic tasks so their imports will be in shared memory
+for name, options in settings.DISPATCHER_SCHEDULE.items():
+    resolve_callable(options['task'])
+
+
+# Preload in-line import from tasks
+from awx.main.scheduler.kubernetes import PodManager  # noqa
+
+
+from django.core.cache import cache as django_cache
+from django.db import connection
+
+connection.close()
+django_cache.close()