workflow: Do not touch dict during iteration
workflow: Do not touch dict during iteration

Django 3.2 stored the field information as dict instead OrderedDict
because python 3.7+ ensure the field order of dict as the language spec.
We cannot touch dict itself during iteration. We need to pass a list
instead of a value from .items() itself to avoid the error.

Change-Id: Ie22865995d14fa60c16cf2cea582aa0eec46b65d
Closes-Bug: #1944548

openstack/horizon,openstack/horizon,openstack/horizon,ChameleonCloud/horizon,openstack/horizon,ChameleonCloud/horizon,ChameleonCloud/horizon,ChameleonCloud/horizon