Timing issue with oneway request example on cxf

Problem found when testing the oneway request fix on CXF.

The integration test sends a oneway request followed by a req/resp - however the req/resp consistently arrives first and gets buffered, while the oneway request is then processed.

However when the req/resp is then processed, it results in the process instance data being deleted prior to the response being returned. As part of returning the response, it attempts to access the header information for the message, which accesses the db, but fails to retrieve header info for the process instance as it has been deleted.