search helper performance improvements

test plan: simple regression test on search functionality
  on course People page

fixes CNVS-15507

Change-Id: I6bdf9a668a232c55e565d6085eeb63776f68c1a6
Reviewed-on: https://gerrit.instructure.com/45548
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: James Williams  <jamesw@instructure.com>
QA-Review: Jahnavi Yetukuri <jyetukuri@instructure.com>
Product-Review: Jeremy Stanley <jeremy@instructure.com>