Add an ensure_image to make sure a docker image exists
Add an ensure_image to make sure a docker image exists

RickyCook/DockCI,RickyCook/DockCI,sprucedev/DockCI-Agent,sprucedev/DockCI,sprucedev/DockCI,sprucedev/DockCI-Agent,RickyCook/DockCI,sprucedev/DockCI,RickyCook/DockCI,sprucedev/DockCI