Fix resetting of access level when updating workflow

If the access level needed to update a Threshold has been changed from
default, it is reset to that default value when the workflow
configuration is updated again without changes to that Threshold.

This commit fixes the incorrect behavior by applying the same mechanism
used to detect a change in the status to the access level, i.e.
comparing the updated access level with the parent and not the current
value.

Fixes 0016771