BZ1123703: Created Spring JTA SharedEM test

Added unit test for Spring, JTA, and Shared Entity Manager with the audit log service.  This reproduces the issues in BZ1123703.
The idea of the shared entity manager is that user will have transactions that span the persistence of JBPM entities as well as their own, within the same entity manager and transaction. I was simulating the transaction boundaries that would be set by a `@Transactional` annotation on a service class/method.  When using Spring and JTA a user would typically not directly access the transaction, and Spring would own the transaction lifecycle.   

Is the problem just with writing process instances, and reading from the audit log service in a single tx?  

Many users/customers won't know about this constraint - Is there any way to prevent the race condition in JBPM?