Description of problem:
If is morphed activity (which contains boundary event already) to script task, boundary event is not removed.

Version-Release number of selected component (if applicable):
jbds-9.1.0.CR1_jbdsis-9.0.0.CR1
jbtis-4.3.0.CR1

Steps to Reproduce:
1. Create manual task in bpmn2 process
2. Add boundary event to manual task from previous step
3. Morph manual task from step 1. to script task

Actual results:
Script task will contain boundary event

Expected results:
Script task will not contain boundary event