Fix manual variable infinite polling

When landing on the manual variable page, you are one the form to run the variable, but the polling for logs is already started 😱 We need to only start polling after the user has run the job.

It probably behave this way because we do not differentiate on the FE between manual and normal jobs.

Then the other part would be to stop polling after the job is completed.

We might also want to look into etags here to cache requests when nothing has changed.