Revert "builder/virtualbox: Copy ISO because VirtualBox can't recognize"

This reverts commit 688be43811007d33b9c70dec93b43782a4f71c06; instead
of copying the ISO (which can be huge), we have adjusted the cache path
to include the extension of the source file.

Conflicts:

	builder/virtualbox/step_download_iso.go

builder/virtualbox/step_download_iso.go

@@ -6,11 +6,7 @@ import (
 	"github.com/mitchellh/multistep"
 	"github.com/mitchellh/packer/builder/common"
 	"github.com/mitchellh/packer/packer"
-	"io"
-	"io/ioutil"
 	"log"
-	"os"
-	"path/filepath"
 	"time"
 )
 
@@ -23,11 +19,9 @@ import (
 //
 // Produces:
 //   iso_path string
-type stepDownloadISO struct {
-	isoCopyDir string
-}
+type stepDownloadISO struct{}
 
-func (s *stepDownloadISO) Run(state map[string]interface{}) multistep.StepAction {
+func (s stepDownloadISO) Run(state map[string]interface{}) multistep.StepAction {
 	cache := state["cache"].(packer.Cache)
 	config := state["config"].(*config)
 	ui := state["ui"].(packer.Ui)
@@ -84,44 +78,10 @@ DownloadWaitLoop:
 		}
 	}
 
-	// VirtualBox is really dumb and can't figure out that the file is an
-	// ISO unless it has a ".iso" extension. We can't modify the cache
-	// filenames so we just do a copy.
-	tempdir, err := ioutil.TempDir("", "packer")
-	if err != nil {
-		state["error"] = fmt.Errorf("Error copying ISO: %s", err)
-		return multistep.ActionHalt
-	}
-	s.isoCopyDir = tempdir
-
-	f, err := os.Create(filepath.Join(tempdir, "image.iso"))
-	if err != nil {
-		state["error"] = fmt.Errorf("Error copying ISO: %s", err)
-		return multistep.ActionHalt
-	}
-	defer f.Close()
-
-	sourceF, err := os.Open(cachePath)
-	if err != nil {
-		state["error"] = fmt.Errorf("Error copying ISO: %s", err)
-		return multistep.ActionHalt
-	}
-	defer sourceF.Close()
-
-	log.Printf("Copying ISO to temp location: %s", tempdir)
-	if _, err := io.Copy(f, sourceF); err != nil {
-		state["error"] = fmt.Errorf("Error copying ISO: %s", err)
-		return multistep.ActionHalt
-	}
-
 	log.Printf("Path to ISO on disk: %s", cachePath)
-	state["iso_path"] = f.Name()
+	state["iso_path"] = cachePath
 
 	return multistep.ActionContinue
 }
 
-func (s *stepDownloadISO) Cleanup(map[string]interface{}) {
-	if s.isoCopyDir != "" {
-		os.RemoveAll(s.isoCopyDir)
-	}
-}
+func (stepDownloadISO) Cleanup(map[string]interface{}) {}