Add yellow/unstable build as a failure

Merged Drew Blessing requested to merge fix_jenkins_status into master

Jenkins has more build statuses than any 'CI' tool I've ever seen. Apparently a build can be 'successful' but if tests fail it's called 'unstable'. However, 'unstable' is not considered a failing build. Bleh...

Anyway, GitLab needs to consider unstable or yellow builds a failure for CI purposes.