Never ending exception loop when shutting down executor thread which runs many processes with timers

Never ending exception loop when shutting down executor thread which runs many processes with timers. I have found this using process flood project for performance testing. PerfCake framework uses executor threads for sender, in this case just one thread was enough. Measurement is fine. When the PerfCake wants to stop measurement (stop executor thread), then never ending loop of transaction errors and warns occurs. Whole log is attached.

2013-10-15 14:44:53,418 WARN [org.drools.persistence.jta.JtaTransactionManager] Unable to begin transaction
bitronix.tm.internal.BitronixSystemException: cannot start a new transaction, transaction manager is shutting down
...
2013-10-15 14:44:53,419 WARN [org.drools.persistence.SingleSessionCommandService] Could not commit session
java.lang.RuntimeException: Unable to begin transaction
...
2013-10-15 14:44:53,420 WARN [org.drools.persistence.jta.JtaTransactionManager] Unable to rollback transaction
java.lang.IllegalStateException: no transaction started on this thread
...
2013-10-15 14:44:53,420 ERROR [org.drools.persistence.SingleSessionCommandService] Could not rollback
java.lang.RuntimeException: Unable to rollback transaction
...

To reproduce:
1.) git clone git://git.app.eng.bos.redhat.com/jbossqe-process-flood.git
2.) cd jbossqe-process-flood/bpms-6.x
3.) ./execute_scenario.sh -Dscenario=Timer_Java -s ../mysql-localhost.xml
Make sure that you have empty MySQL database accessible via properties defined in mysql-localhost.xml file.
4.) Never ending loop runs. Shut it down with Ctrl+C and check the log file:
less perfcake.log

My environment:
BPMS 6 ER4 (6.0.0-redhat-4)
PerfCake 1.0 (available in maven central)
MySQL 5.5.32
Singleton runtime manager, single thread