properly quoted display name in outgoing email

fixes CNVS-14790

test plan
- set up a custom 'From' name with a ':' in it
- cause an email to be sent from that account
- ensure that the email is sent

Change-Id: Id3a3179dd9b9f17a05c8cb4c7cf3fba57b59c87c
Reviewed-on: https://gerrit.instructure.com/39319
Reviewed-by: Cody Cutrer <cody@instructure.com>
Tested-by: Jenkins <jenkins@instructure.com>
QA-Review: August Thornton <august@instructure.com>
Product-Review: Cody Cutrer <cody@instructure.com>