Merge behaviour of cancel and terminate workflows

gso/translations/en-GB.json

gso/workflows/__init__.py

gso/workflows/iptrunk/terminate_iptrunk.py

gso/workflows/router/terminate_router.py

gso/workflows/shared/__init__.py

gso/workflows/shared/cancel_subscription.py

gso/workflows/site/terminate_site.py

test/workflows/iptrunk/test_terminate_iptrunk.py

test/workflows/router/test_terminate_router.py

test/workflows/shared/__init__.py

test/workflows/shared/cancel_subscription.py