Add a basic rollback accumlator test.
Add a basic rollback accumlator test.

pombredanne/taskflow-1,citrix-openstack-build/taskflow,jimbobhickville/taskflow,jimbobhickville/taskflow,openstack/taskflow,jessicalucci/TaskManagement,citrix-openstack-build/taskflow,junneyang/taskflow,junneyang/taskflow,pombredanne/taskflow-1,varunarya10/taskflow,jessicalucci/TaskManagement,openstack/taskflow,varunarya10/taskflow