update acceptance/box_test

Some minor change to reflect new outputs of some "vagrant box" commands. (add, repackage)

I've marked the test to verify a box to pending because I don't know if the Virtualbox plugin is ready to verify a box.

Also be aware that I've done my tests with a default.box which contains a "Vagrant.configure("2")" line in Vagrantfile and a metadata.json file. If you don't add this file the test about repackaging your box may fail because of a size difference

All acceptance tests of box_test.rb should pass now.