JBPM-3951 - 'java.lang.IllegalArgumentException: No interfaces found', whereas xml is valid according to BPMN2 schema
JBPM-4335 - WorkItem can't be linked to throwing Message Event which created it
BZ-1101433 - CNFE when calling getContent via remote api for Custom Objects - removed content unmarshalling from JAXBContent object

(cherry picked from commit 25237d068629b93d30a734e979121478a1cf1c6c)