spec: speed up api specs

liberal applicataion of once-ler and bulk_insert helpers, reduce runtime
from 50min -> 25min

Change-Id: I07c1952c4ead0a1c6caafc389de0b9586b27dc68
Reviewed-on: https://gerrit.instructure.com/37794
Reviewed-by: Landon Wilkins <lwilkins@instructure.com>
Tested-by: Jenkins <jenkins@instructure.com>
Product-Review: Jon Jensen <jon@instructure.com>
QA-Review: Jon Jensen <jon@instructure.com>