a8n: When retrying Campaign creation only retry failed jobs

Created by: mrnugget

This was an oversight on my part. I didn't check the opposite case in the test.

The bug manifested itself in that we retried every job when retrying Campaign creation, even the ones that successfully created a changeset on a codehost. That wasn't a huge problem since that function is idempotent, but it's still needless work and the behavior of the method doesn't match its name.