Add logic around vmware specific clause

- Really temporary fix for suckers in the team who aren't lucky enough to have :money_with)wings: vmware :money_with_wings: as their vm provider
- It's difficult to switch on current provider in your vagrantfile, there are some workarounds listed here: https://github.com/mitchellh/vagrant/issues/1867
- Will have a bash at refactoring to match some of those solutions, but this temporarily fixes this issue: http://cl.ly/image/0n0m0E1F3b2y
Merge pull request #629 from alphagov/notallvms

Add logic around vmware specific clause