Jenkins integration appears to be broken after !9

• GitLab version: 8.0.1-ee
• Zendesk ticket: https://gitlab.zendesk.com/agent/tickets/8612

Description of issue

After !9 (merged) was merged and the customer upgraded to 8.0, their Jenkins integration broke. GitLab is now unable to fetch the build status of the merge request. It always returns an error. Going into Jenkins directly to check on the status of the build yields the expected images on which the status fetching is based.

Reverting the commits in !9 (merged) solves the problem.

This is what the customer said about it:

This MR has added mandated support for generating a custom jenkins job for each build, which is optional and not something we use.

This commit should be reverted pending a fix that creates a setting to enable this.

Result of replication

I don't have a Jenkins server, so I cannot replicate.

Concrete questions / Next steps

@dzaporozhets you approved !9 (merged), can you take a look and see what needs fixing?

/cc @JobV