group-detach does not add correct objectclasses

https://fedorahosted.org/freeipa/ticket/4874

Reviewed-By: Rob Crittenden <rcritten@redhat.com>
Reviewed-By: Petr Vobornik <pvoborni@redhat.com>

ipalib/plugins/group.py

@@ -653,6 +653,7 @@ class group_detach(LDAPQuery):
         objectclasses = list(set(def_objectclass + objectclasses))
 
         group_attrs['mepManagedBy'] = None
+        group_attrs['objectclass'] = objectclasses
         ldap.update_entry(group_attrs)
 
         return dict(