fix selenium encrypted_cookie_store resetting for rails 3

Change-Id: I457a8d04e2e8fe2e4f16ee32dbff63897509f8b8
Reviewed-on: https://gerrit.instructure.com/30149
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Cody Cutrer <cody@instructure.com>
Product-Review: James Williams  <jamesw@instructure.com>
QA-Review: James Williams  <jamesw@instructure.com>