Use prepared model and scripts if exist

Change-Id: I9186ad365f5f3f330a11930fecd0e18fd7465ae0
diff --git a/day01-image/run.example.sh b/day01-image/run.example.sh
index 6732787..bc4a811 100755
--- a/day01-image/run.example.sh
+++ b/day01-image/run.example.sh
@@ -34,20 +34,22 @@
 
 export PACKER_LOG=1
 pushd config-drive
-  [ -d model ] && rm -rf model
-  git clone ${CLUSTER_MODEL} model/
-  pushd model
-    git fetch ${CLUSTER_MODEL} ${CLUSTER_MODEL_REF} && git checkout FETCH_HEAD
-    pushd classes/system
-      git submodule init
-      git submodule update
+  if [ ! -e model ]; then
+    git clone ${CLUSTER_MODEL} model/
+    pushd model
+      git fetch ${CLUSTER_MODEL} ${CLUSTER_MODEL_REF} && git checkout FETCH_HEAD
+      pushd classes/system
+        git submodule init
+        git submodule update
+      popd
     popd
-  popd
-  [ -d salt_scripts ] && rm -rf salt_scripts
-  git clone ${GIT_SALT_FORMULAS_SCRIPTS} salt_scripts/
-  pushd salt_scripts
+  fi
+  if [ ! -e salt_scripts ]; then
+    git clone ${GIT_SALT_FORMULAS_SCRIPTS} salt_scripts/
+    pushd salt_scripts
     git fetch ${GIT_SALT_FORMULAS_SCRIPTS} ${SCRIPTS_REF} && git checkout FETCH_HEAD
-  popd
+    popd
+  fi
 popd
 
 [ -f config-drive/cloudata.iso ] && rm -v config-drive/cloudata.iso