fix peer review notification links

fixes CNVS-15257

test plan
- cause a peer review notification to be sent from an account with
 a domain name other than the default
- ensure that the links in the notification use the correct domain

Change-Id: Ia0042367317aab3308bc2c8c82138ee1de22f22a
Reviewed-on: https://gerrit.instructure.com/42108
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Mark Severson <markse@instructure.com>
QA-Review: Steven Shepherd <sshepherd@instructure.com>
Product-Review: Joel Hough <joel@instructure.com>