Fix and enhance Neo4j transaction handling in all instances

[yuanzhou]

• Initialize tx = None before the try block
• Add check tx is not None in the exception handler
• Add a catch-all except Exception as e: clause for full coverage
• Update the consumer methods to properly catch the new Exception if not already in place

Found 10 usage instances: https://github.com/search?q=repo%3Ahubmapconsortium%2Fentity-api%20tx.rollback()&type=code