Modernize function and method attribute names

Python 3 uses double-underscored names for internal function attributes.
In Python 2.7, these names exist as aliases to the old 'func_*' and
'im_*' names.

Reviewed-By: Tomas Babej <tbabej@redhat.com>

ipalib/plugins/permission.py

@@ -1194,7 +1194,7 @@ class permission_mod(baseldap.LDAPUpdate):
         return dn
 
     def exc_callback(self, keys, options, exc, call_func, *call_args, **call_kwargs):
-        if call_func.func_name == 'update_entry':
+        if call_func.__name__ == 'update_entry':
             self._revert_aci()
         raise exc