enable parallelized_specs in rails3

Change-Id: I40501f963b9c0b634ab1f0eb79ae5c443fa7cb13
Signed-off-by: Stephan Hagemann <stephanh@instructure.com>
Reviewed-on: https://gerrit.instructure.com/28516
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Bryan Madsen <bryan@instructure.com>
QA-Review: Bryan Madsen <bryan@instructure.com>
Product-Review: Bryan Madsen <bryan@instructure.com>