add a new EBS volume to setup.sh for the analytics machine

Summary:
This volume was manually attached and mounted, but these changes serve
as documentation and the keep the setup current in case we need to re-create
or clone the analytics machine.

Test Plan: The commands in this change were also performed manually by me.

Reviewers: eliana

Differential Revision: http://phabricator.khanacademy.org/D2376