Creation still in progress fixups

This should help with the recent increase in `Plines::JobBatch::CreationInStillInProgressError` errors we've been getting.  It won't cause the underlying problem causing the increase but will make it a bit less common (since 6 hours was too long of a timeout to begin with) and will log the reason the job batch creation got aborted, helping us to better understand the root cause.
I don't think it's something that consumers of plines want to consciously think about and change from the default.  6 hours was clearly too long and 1 hour is still plenty long -- there's no way a job batch will take longer than an hour to be created.