BZ-1071144 - BPMS cluster with deployment unit using PER_PROCESS_INSTANCE session strategy throws java.lang.IllegalStateException

(cherry picked from commit c51414032af8e3cd6654162a10a305fd77fd7e9d)
BZ-1071144 - BPMS cluster with deployment unit using PER_PROCESS_INSTANCE session strategy throws java.lang.IllegalStateException - support for both XmlAttribute and XmlElement

(cherry picked from commit 3d2c255792ad4aeb7d5a006274dd8aecd8e77c71)