I think this is saying that you changed persistence.xml to point to mysql but h2 is still used, what else should be changed?
You might want to look at my question:
https://community.jboss.org/thread/196826
as this includes changes to hibernate.cfg.xml and JBPMorm.xml that others have suggested. This definitely points things at mysql as I can see the tables being created there.
However you will also see it doesn't work...