fix user list e-mail parsing with unicode

test plan:
* use the course users page to add users
with names that include unicode characters
(such as accents)
* should not fail with "unparseable" errors

closes #CNVS-15085

Change-Id: Ieee80adbabed05f42aab8040c4351e35b680a75e
Reviewed-on: https://gerrit.instructure.com/41766
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Jeremy Stanley <jeremy@instructure.com>
Product-Review: Jeremy Stanley <jeremy@instructure.com>
QA-Review: Clare Strong <clare@instructure.com>