remove unused switch_role functionality

this was replaced a long time ago by test student

Change-Id: I20981ada3e72df82da89d5bae1b81a3b31cfac66
Reviewed-on: https://gerrit.instructure.com/36309
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>