middleware.rb

class OnDestroyMiddleware
  def initialize(app, env)
    @app = app
    @env = env
  end

  def call(env)
    provisioners = env[:global_config].vm.provisioners
    chef_provisioners = provisioners.find_all { |p| p.provisioner == Vagrant::Provisioners::ChefClient }
    chef_provisioners.each do |provisioner|
      remove_chef_client provisioner
      remove_chef_node provisioner
    end
    @app.call(env)
  end

  private
  def remove_chef_client(provisioner)
    remove_chef(:client, provisioner)
  end

  def remove_chef_node(provisioner)
    remove_chef(:node, provisioner)
  end

  def remove_chef(subject, provisioner)
    @env[:ui].info "Removing #{subject.to_s} #{provisioner.config.node_name}"
    `bundle exec knife #{subject.to_s} delete #{provisioner.config.node_name} -y`
  end
end

Vagrant.actions[:destroy].use(OnDestroyMiddleware)