JpaStoreOOMETest.testProcessClear always fails

Test history: http://ci.infinispan.org/project.html?projectId=Infinispan&testNameId=-2900853710908128505&tab=testDetails

I think the test might be working with an in-memory H2 database, which would explain the failure. We could try to run the stress tests with another DB (perhaps with the mysql profile).