Job pages poll for traces on unstarted manual jobs
This is very similar to #284103 (closed), but for a slightly different case.
In gitlab-com/gl-infra/scalability#654 (comment 463288209) we found that when a manual job is not started, we'll still poll for the trace - even though there can't be any trace. Here are some requests from a user doing just that: https://log.gprd.gitlab.net/goto/1c12c7fa3037849df1a37ce3e053197f
The job itself was manual and not started:
[ gprd ] production> Ci::Build.find(882474289).started_at
=> nil
[ gprd ] production> Ci::Build.find(882474289).status
=> "manual"
It's easy to reproduce this on a manual job on this project, like this one: https://gitlab.com/gitlab-org/gitlab/-/jobs/900093691