Fix Orphaned Child Models in Workflow Delete

Fix orphaned child models in workflow delete.

Likely related to issue with workflow error if workflow in progress is
deleted.
Fix Typo in WorkflowProgress Model Call

Fix typo from `WorkflowProgess` to `WorkflowProgress`
Merge pull request #965 from mkly/bugfix_fix_orphaned_children_in_workflow_delete

Fix Orphaned Child Models in Workflow Delete