script: add host time sync ntp setup script.

scripts/time_sync.sh

+#!/usr/bin/env bash
+
+###############################################################################
+# Copyright 2017 The Apollo Authors. All Rights Reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+###############################################################################
+
+grep -q ntpdate /etc/crontab
+
+if [ $? -eq 1 ]; then
+    echo "*/1 * * * * root ntpdate -v -u us.pool.ntp.org" | sudo tee -a /etc/crontab
+fi
+
+# ntpdate running log at /var/log/syslog