[berkshelf] Berkshelf is for Workstations

This makes the Vagrant driver behave more like the LXC driver, relying on the SSH Base semantics set forth in test-kitchen@1.0

I prefer to have berkshelf resolve cookbooks on the workstation -- temporarily install them somewhere, and then have an intermediate system, in this case, TK, ship cookbooks and so-on from a combined, resolved, cookbook directory. Previously Vagrant was trying to interact with Berkshelf on the guest, which would mean that the guest would need to have access to Git, etc