Be less verbose while changing the password. Add a script for checking if password already exists.

scripts/image_signing/ensure_no_password.sh

Index: scripts/image_signing/ensure_no_password.sh
diff --git a/scripts/image_signing/ensure_no_password.sh b/scripts/image_signing/ensure_no_password.sh
new file mode 100755
index 0000000000000000000000000000000000000000..5bda0a7b53bc03ef0a713d77e1cf1ff9bdf6faf5
--- /dev/null
+++ b/scripts/image_signing/ensure_no_password.sh
@@ -0,0 +1,25 @@
+#!/bin/bash
+
+# Copyright (c) 2010 The Chromium OS Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+# abort on error
+set -e
+
+# Load common constants and variables.
+. "$(dirname "$0")/common.sh"
+
+if [ $# -ne 1 ]; then
+    echo "Usage $0 <image>"
+    exit 1
+fi
+
+IMAGE=$1
+ROOTFS=$(make_temp_dir)
+mount_image_partition_ro "$IMAGE" 3 "$ROOTFS"
+
+if ! no_chronos_password $rootfs; then
+    echo "chronos password is set! Shouldn't be for release builds."
+    exit 1
+fi