workflows: fix PostgreSQL model compatibility
- Fixes UUID usage on bwlWORKFLOW, bwlWORKFLOWLOGGING tables. (closes #3217)
- Defines a delete cascade action for BibWorkflowObject and BibWorkflowObjectLog if you delete a Workflow.
- Fixes testsuite to properly clean the database after ending. (closes #3147)
Signed-off-by: Leonardo Rossi <leonardo.r@cern.ch>