`Path` para el proveedor de shell no existe en el sistema de host:

Vagrant.configure("2") do |config|

  config.vm.box = "ubuntu/xenial64"

  dir = File.expand_path("..", __FILE__)
  puts "DIR: #{dir}"

  config.vm.provision "shell", path: File.join(dir, "script.sh")

end
Concerned Centipede