Include cache in the state bag.

builder/hyperv/iso/builder.go

@@ -17,9 +17,9 @@ import (
 	"github.com/mitchellh/packer/powershell/hyperv"
 	"github.com/mitchellh/packer/template/interpolate"
 	"log"
+	"os"
 	"strings"
 	"time"
-	"os"
 )
 
 const (
@@ -324,6 +324,7 @@ func (b *Builder) Run(ui packer.Ui, hook packer.Hook, cache packer.Cache) (packe
 
 	// Set up the state.
 	state := new(multistep.BasicStateBag)
+	state.Put("cache", cache)
 	state.Put("config", &b.config)
 	state.Put("driver", driver)
 	state.Put("hook", hook)