Description of problem:
BitronixRollbackException and other exceptions are thrown instead of transaction rollback.

Version-Release number of selected component (if applicable):
jBPM 6.2.0 CR1

How reproducible:
https://gitlab.mw.lab.eng.bos.redhat.com/bxms/brms/blob/master/test-jbpm-regression/src/test/java/com/bpms/customer/BZ958390RuntimeExceptionAfterTimerTest.java
https://gitlab.mw.lab.eng.bos.redhat.com/bxms/brms/blob/master/test-jbpm-regression/src/test/resources/com/bpms/customer/RuntimeExceptionAfterTimer.bpmn2

Steps to Reproduce:
1. Create a process with intermediate timer event and throw exception after it.
2. Run the process and see the results.

Actual results:
A lot of different exceptions are thrown.

Expected results:
The transaction rollback should be performed without any problems.

Additional info:
This issue was introduced between versions Beta3 and CR1, and it might be related to bug 958390.