add vagrant style build for go_segment

This PR is to build a base box for go_segment to speed up our Jenkins build times. We were not able to get the packer approach to building boxes working, because of the private SG cookbooks. Instead we used Vagrant, Berkshelf, and `vagrant package` to build the box, see the README in `go_segment_base` directory.

Let me know if there are questions or feeback, or if you prefer I PR this to a topic branch since it's so different.
I think packer must have the virtual disk in the virtualbox image not under the 0 directory, so I think we need to look in both places for vmdk files.  As long as we're doing that we should probably find them all, print a warning if there are > 1, print an error and exit if there are < 1.