rails3: fix erubis for messages

it's weird/scary that this wasn't an issue for the message tests

Change-Id: I2189eb1f39c3613735fc13beeb4d997f4f9a71cb
Reviewed-on: https://gerrit.instructure.com/29924
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Jon Willesen <jonw@instructure.com>
Product-Review: Cameron Matheson <cameron@instructure.com>
QA-Review: Cameron Matheson <cameron@instructure.com>