parallelize summarymessageconsolidator job

Change-Id: I91c9efefa46436b714954cac282464c8190410ae
Reviewed-on: https://gerrit.instructure.com/30398
Reviewed-by: Braden Anderson <banderson@instructure.com>
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Jacob Fugal <jacob@instructure.com>
Product-Review: Cody Cutrer <cody@instructure.com>
QA-Review: Cody Cutrer <cody@instructure.com>