Use shared '_check' function to check engine stages
Use shared '_check' function to check engine stages

Change-Id: I48e5efdb28ee834666ec1eca18f35f245de340d3

openstack/taskflow,openstack/taskflow,junneyang/taskflow,jimbobhickville/taskflow,junneyang/taskflow,pombredanne/taskflow-1,jimbobhickville/taskflow,pombredanne/taskflow-1