Fix list_modules for PackageLoader

jinja2/loaders.py

@@ -251,8 +251,7 @@ def _walk(path):
             for filename in self.provider.resource_listdir(path):
                 fullname = path + '/' + filename
                 if self.provider.resource_isdir(fullname):
-                    for item in _walk(fullname):
-                        results.append(item)
+                    _walk(fullname)
                 else:
                     results.append(fullname[offset:].lstrip('/'))
         _walk(path)