spec: intermittent file_spec fix

Change-Id: I5d56f1d5f689d35add03ac143c090ef10c8cef87
Reviewed-on: https://gerrit.instructure.com/29066
Reviewed-by: Dave Jungst <dave@instructure.com>
Product-Review: Dave Jungst <dave@instructure.com>
QA-Review: Dave Jungst <dave@instructure.com>
Tested-by: Dave Jungst <dave@instructure.com>
Tested-by: Jenkins <jenkins@instructure.com>