Merge pull request #5005 from hashicorp/fix5004

vagrant-cloud: use less memory when uploading

post-processor/vagrant-cloud/client.go

@@ -108,17 +108,15 @@ func (v VagrantCloudClient) Upload(path string, url string) (*http.Response, err
 		return nil, fmt.Errorf("Error opening file for upload: %s", err)
 	}
 
-	defer file.Close()
-
-	body := &bytes.Buffer{}
-
-	_, err = io.Copy(body, file)
+	fi, err := file.Stat()
 
 	if err != nil {
-		return nil, fmt.Errorf("Error uploading file: %s", err)
+		return nil, fmt.Errorf("Error stating file for upload: %s", err)
 	}
 
-	request, err := http.NewRequest("PUT", url, body)
+	defer file.Close()
+
+	request, err := http.NewRequest("PUT", url, file)
 
 	if err != nil {
 		return nil, fmt.Errorf("Error preparing upload request: %s", err)
@@ -126,6 +124,7 @@ func (v VagrantCloudClient) Upload(path string, url string) (*http.Response, err
 
 	log.Printf("Post-Processor Vagrant Cloud API Upload: %s %s", path, url)
 
+	request.ContentLength = fi.Size()
 	resp, err := v.client.Do(request)
 
 	log.Printf("Post-Processor Vagrant Cloud Upload Response: \n\n%+v", resp)