ubuntu16.04 parametrize saltstack

Change-Id: I11f47e94c49112a862634099562c86afb77bed14
diff --git a/ubuntu-16.04/template.json b/ubuntu-16.04/template.json
index 6d0e1fc..467b143 100644
--- a/ubuntu-16.04/template.json
+++ b/ubuntu-16.04/template.json
@@ -5,7 +5,8 @@
     "distro": "ubuntu-16-04-x64",
     "disk_size": "8000",
     "ubuntu_baseurl": "https://mirror.mirantis.com/proposed/ubuntu/",
-    "saltstack_repo": "deb [arch=amd64] https://mirror.mirantis.com/proposed/saltstack-2016.3/xenial/ xenial main",
+    "saltstack_gpg": "{{ env `SALTSTACK_GPG` }}",
+    "saltstack_repo": "{{ env `SALTSTACK_REPO` }}",
     "do_api_token": "{{ env `DO_API_TOKEN` }}",
     "image_name": "{{ env `IMAGE_NAME` }}",
     "os_username": "{{ env `OS_USERNAME` }}",