Fixed ansible custom promise type ability to load modules

This seems to be due to the promise type not calling init_plugin_loader() as mentioned in this issue:
ansible/ansible#83992 and solved in this
commit ansible/ansible-documentation#1524
This occurred with the upgrade from ansible 2.14 to 2.15 around May 2024.

Ticket: ENT-13701
Changelog: title

Author: craigcomstock

promise-types/ansible/ansible_promise.py

@@ -13,6 +13,7 @@
     from ansible.parsing.dataloader import DataLoader
     from ansible.plugins.callback import CallbackBase
     from ansible.vars.manager import VariableManager
+    from ansible.plugins.loader import init_plugin_loader
 
     ANSIBLE_AVAILABLE = True
 except ImportError:
@@ -165,4 +166,5 @@ def evaluate_promise(
 
 
 if __name__ == "__main__":
+    init_plugin_loader()
     AnsiblePromiseTypeModule().start()