fix rails 3 spec mocking

if mocha was initialized prior to rails (i.e. if a spec like swagger
that doesn't initialize rails runs prior to a spec that needs rails),
CollectionProxy would remove the mocha methods when it was first defined.
so make sure we restore them

Change-Id: Icf9b1a2598fef279c32b37dd7afe52e15c07c23e
Reviewed-on: https://gerrit.instructure.com/31934
Tested-by: Jenkins <jenkins@instructure.com>
Product-Review: Bryan Madsen <bryan@instructure.com>
QA-Review: Bryan Madsen <bryan@instructure.com>
Reviewed-by: Cameron Matheson <cameron@instructure.com>