Added Vagrantfile for search-rpc server.

Summary:
Run `vagrant up` to bring up server. Solr will be available at
localhost:9001. The secret is "secret".

Test Plan:
Tested with clean install (no box and then running `vagrant up`)
and also repeatedly provisioned with `vagrant provision`.
Checked afterwards each time with SOLR_URL patched code to make
sure indexing completes without errors.

Reviewers: dylan

Reviewed By: dylan

Differential Revision: http://phabricator.khanacademy.org/D7835