We're currently requiring it twice: in image_info and in a separate
configdrive argument. I think we should eventually settle on separate
arguments for separate entities, so this change makes the value in
image_info optional with a goal to stop accepting it.
We could probably just remove the handling in image_info, but a
deprecation is safer.
The (unused in ironic) cache_image call is updated with an optional
configdrive arguments.
Story: #2008904
Task: #42480
Change-Id: I1e2efa28efa3ea7e389774cb7633d916757bc6ed