Add Vagrantfile for quickly testing Packer builds

Allows testing box with `vagrant up <name>` after a build, without
having to do a manual `vagrant box add` and defining a Vagrantfile
that boots the newly added box.

Change-Id: Ib9b232daf55901169535823f6f71cd0d7b30e524
Signed-off-by: Daniel Farrell <dfarrell@redhat.com>