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.env b/day01-image/template.json.env
new file mode 100644
index 0000000..fb05cc3
--- /dev/null
+++ b/day01-image/template.json.env
@@ -0,0 +1 @@
+PACKER_IMAGES_CACHE="${HOME}/packer_images_cache/"