Returns correct errors from 2.2.6+ versions of Neo4j

In 2.2.6 a change was made to make a transaction that had a ClientError automatically rollback, (see neo4j/neo4j#5806). When a client performed a rollback itself (as Neo4jClient does) this resulted in a 404 error due to the fact that the Transaction was no longer there.

This release returns Neo4jClient to acting the way it used to - by returning the actual error.

You will still get the 404 response but only if an actual Timeout has occurred.