have to update mysql2 for rails3

Change-Id: I3370986b7ab335f3383c2f3b565918086280fda9
Reviewed-on: https://gerrit.instructure.com/32276
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: James Williams  <jamesw@instructure.com>
Product-Review: Cody Cutrer <cody@instructure.com>
QA-Review: Cody Cutrer <cody@instructure.com>