pylint: Fix modified-iterating-list
    
    https://pylint.pycqa.org/en/latest/user_guide/messages/warning/modified-iterating-list.html:
    > Emitted when items are added or removed to a list being iterated
    through. Doing so can result in unexpected behaviour, that is why it is
    preferred to use a copy of the list.
    
    https://docs.python.org/3/tutorial/controlflow.html#for-statements:
    > Code that modifies a collection while iterating over that same
    collection can be tricky to get right. Instead, it is usually more
    straight-forward to loop over a copy of the collection or to create a
    new collection
    
    Fixes: https://pagure.io/freeipa/issue/9278
    Signed-off-by: Stanislav Levin <slev@altlinux.org>
    Reviewed-By: Stanislav Levin <slev@altlinux.org>