crocodoc: retry more frequently

closes CNVS-7104, closes CNVS-12396

Test plan:
  Developers could test this but it would be hard for QA to do anything
  on this one.

Change-Id: Ieab9326a4e2a45264894e201e839568d813cbe57
Reviewed-on: https://gerrit.instructure.com/33319
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Simon Williams <simon@instructure.com>
QA-Review: Amber Taniuchi <amber@instructure.com>
Product-Review: Cameron Matheson <cameron@instructure.com>