fix bad users.id query on masquerade

closes CNVS-4747

Change-Id: I9aa6b3e566c1f471a8da86aad66c3197c128caa3
Reviewed-on: https://gerrit.instructure.com/31705
Reviewed-by: Cody Cutrer <cody@instructure.com>
Tested-by: Jenkins <jenkins@instructure.com>
Product-Review: Rob Orton <rob@instructure.com>
QA-Review: Rob Orton <rob@instructure.com>