[jennyd] Use latest VirtualBox 4.2

When bringing up a new dev VM using all the defaults from gds_development,
I got the error described here after the image had finished downloading:

    https://github.com/phusion/open-vagrant-boxes/issues/1

Upgrading VirtualBox to 4.2.22 (from 4.2.6, the recommended version in
gds_development) seems to solve this issue.