Fix Inventory Plugin Loading (#31605)

This change makes the PluginLoader use DEFAULT_INVENTORY_PLUGIN_PATH setting.
Inventory Plugins were only being loaded the 'inventory_plugins' folder of the current directory,
as well as the ansible-provided inventory plugins (e.g. `/path/to/site-packages/ansible/plugins/inventory`).

lib/ansible/inventory/manager.py

@@ -177,7 +177,7 @@ class InventoryManager(object):
     def _setup_inventory_plugins(self):
         ''' sets up loaded inventory plugins for usage '''
 
-        inventory_loader = PluginLoader('InventoryModule', 'ansible.plugins.inventory', 'inventory_plugins', 'inventory_plugins')
+        inventory_loader = PluginLoader('InventoryModule', 'ansible.plugins.inventory', C.DEFAULT_INVENTORY_PLUGIN_PATH, 'inventory_plugins')
         display.vvvv('setting up inventory plugins')
 
         for name in C.INVENTORY_ENABLED: