Add proper qemu-caching for source image

  * Require command at slaves:
    'mkdir -p "${HOME}/packer_images_cache/"'
    since packer not able to do it.
  * set SALT_STOPSTART_WAIT=10 for salt bootstrap
  * Dd iptables to base installation

Change-Id: Icc5a50a21e848b93660aa80483b6fdd3e27de243
diff --git a/day01-image/template.json b/day01-image/template.json
index 1406680..c4ff8de 100644
--- a/day01-image/template.json
+++ b/day01-image/template.json
@@ -2,6 +2,8 @@
   "variables": {
     "user": "root",
     "password": "r00tme",
+    "images_cache": "{{ env `PACKER_IMAGES_CACHE` }}",
+    "disk_size": "50000",
     "do_api_token": "{{ env `DO_API_TOKEN` }}",
     "image_name": "{{ env `IMAGE_NAME` }}",
     "cluster_model": "{{ env `CLUSTER_MODEL` }}",
@@ -17,8 +19,7 @@
     "apt_mirantis_salt_repo": "{{ env `APT_MIRANTIS_SALT_REPO` }}",
     "git_salt_formulas_scripts": "{{ env `GIT_SALT_FORMULAS_SCRIPTS` }}",
     "apt_repository": "{{ env `APT_REPOSITORY` }}",
-    "apt_repository_gpg": "{{ env `APT_REPOSITORY_GPG` }}",
-    "disk_size": "50000"
+    "apt_repository_gpg": "{{ env `APT_REPOSITORY_GPG` }}"
 
   },
   "provisioners": [
@@ -125,6 +126,7 @@
       "iso_checksum": "566efef1d6f12e7d3a994c2405bdb642",
       "iso_checksum_type": "md5",
       "iso_url": "http://cloud-images.ubuntu.com/releases/xenial/release-20180306/ubuntu-16.04-server-cloudimg-amd64-disk1.img",
+      "iso_target_path": "{{ user `images_cache`}}/release-20180306_xenial-server-cloudimg-amd64-disk1.img",
       "disk_image": true,
       "accelerator": "kvm",
       "disk_size": "{{ user `disk_size`}}",