don't disconnect the database during tests

Change-Id: I7e182abf124324c7f449adcd1ceb3efbf7c78d8c
Reviewed-on: https://gerrit.instructure.com/30378
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Derek DeVries <ddevries@instructure.com>
Product-Review: Cody Cutrer <cody@instructure.com>
QA-Review: Cody Cutrer <cody@instructure.com>