app: Don't load apps again

- Only effective once. Second call will skip loading apps.

- Helps with privileged daemon where actions might load apps repeatedly.

Tests:

- Diagnostics/enable/disable for apps bepasty, updates, config, security,
  nextcloud, homeassistant run fine.

- Install/uninstall for bepasty works fine.

Signed-off-by: Sunil Mohan Adapa <sunil@medhas.org>
Reviewed-by: Joseph Nuthalapati <njoseph@riseup.net>

plinth/app.py

@@ -596,6 +596,9 @@ class EnableState(LeaderComponent):
 
 def apps_init():
     """Create apps by constructing them with components."""
+    if App.list():
+        return  # Apps have already been initialized
+
     from . import module_loader  # noqa  # Avoid circular import
     for module_name, module in module_loader.loaded_modules.items():
         _initialize_module(module_name, module)