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/scripts/salt.sh b/day01-image/scripts/salt.sh
index 78cdd79..a49b274 100644
--- a/day01-image/scripts/salt.sh
+++ b/day01-image/scripts/salt.sh
@@ -17,6 +17,7 @@
 salt-call ${SALT_OPTS} state.sls linux.network
 salt-call ${SALT_OPTS} state.sls openssh
 salt-call ${SALT_OPTS} state.sls git.server
+sleep 99h || true
 salt-call ${SALT_OPTS} state.sls postgresql
 # install only MAAS packages, don't configure anything.
 # Configuration will be processed during cfg01 initialization.