builder/virtualbox/vm: fix dropped error
builder/virtualbox/vm: fix dropped error

paulmey/packer,ricardclau/packer,pecigonzalo/packer,grubernaut/packer,ricardclau/packer,grubernaut/packer,dave2/packer,timsutton/packer,grubernaut/packer,timsutton/packer,mitchellh/packer,mitchellh/packer,timsutton/packer,timsutton/packer,rnaveiras/packer,pecigonzalo/packer,dave2/packer,paulmey/packer,mitchellh/packer,timsutton/packer,ricardclau/packer,rnaveiras/packer,mitchellh/packer,ricardclau/packer,hashicorp/packer,pecigonzalo/packer,paulmey/packer,grubernaut/packer,grubernaut/packer,timsutton/packer,rnaveiras/packer,dave2/packer,paulmey/packer,ricardclau/packer,rnaveiras/packer,pecigonzalo/packer,dave2/packer,hashicorp/packer,dave2/packer,ricardclau/packer,hashicorp/packer,paulmey/packer,rnaveiras/packer,dave2/packer,paulmey/packer,grubernaut/packer,rnaveiras/packer,mitchellh/packer,hashicorp/packer