update vmware tools install script for packer 0.5

Building on #3 

I noticed that vmware tools don't install with Packer 0.5. This manifests itself as HGFS kernel errors when doing a `vagrant up`.

This PR changes the vmware detection logic to match the start of the `PACKER_BUILDER_TYPE` string so it should be backwards compatible and work with both of the new provisioners.

https://github.com/mitchellh/packer/blob/master/CHANGELOG.md#050-12302013