Revert "GRAILS-11687 hibernate4: fix hibernate.flush.mode setting doesn't work outside OSIV session"

This reverts commit 19d8f640930282d0bfb4eecefaa626cf19df022d.
Revert "GRAILS-11687 hibernate3: fix hibernate.flush.mode setting doesn't work outside OSIV session"

This reverts commit 58d9829743a569856a7695d409fe3b411eddbc75.