Trim the image when creating a k8s job

I found this issue in the dashboard:

(combined from similar events): Error creating: Pod "grader-*******" is invalid: spec.initContainers[1].image: Invalid value: "******* ": must not have leading or trailing whitespace

Note: for privacy reasons, I've hidden the id of the job and tha actual name of the image, but we can still see the trailing whitespace