Jenkins should always reject a diff first.
Jenkins should always reject a diff first.

Summary:
This should avoid situations when Jenkins fails to report success or
failure.

Test Plan: pipeline

Reviewers: zen-dog, kensipe, jenkins, wavesoft

Reviewed By: kensipe, jenkins, wavesoft

Subscribers: wavesoft, marathon-team, marathon-dev, jenkins

Differential Revision: https://phabricator.mesosphere.com/D881

guenter/marathon,guenter/marathon,mesosphere/marathon,guenter/marathon,janisz/marathon,Caerostris/marathon,gsantovena/marathon,meln1k/marathon,janisz/marathon,meln1k/marathon,gsantovena/marathon,meln1k/marathon,mesosphere/marathon,janisz/marathon,Caerostris/marathon,meln1k/marathon,guenter/marathon,guenter/marathon,Caerostris/marathon,gsantovena/marathon,Caerostris/marathon,janisz/marathon,gsantovena/marathon,meln1k/marathon,mesosphere/marathon,mesosphere/marathon,Caerostris/marathon,gsantovena/marathon,janisz/marathon,mesosphere/marathon