provisioner/shell: fix dropped error
provisioner/shell: fix dropped error

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