JBSEAM-4840 aplied JAVASSIST fix for JASSIST-66
Improving JBSEAM-4375

When we flush the nested conversation in order to be able to switch to parent conversation,
we passivate Entities that are stored in the nested conversation, but when we go back to the nested
conversation we never activate then again, leaving blank EntityBeanList all over the place.

This could trigger hard to debug problems (for example, an unused injection was removed and then the whole page
stopped working due to NPEs inside Entity Lists)