Add an ntp element

It is quite painful to debug issues across hosts without time sync.

Partial-Bug: #1184486
Change-Id: I149b30d76690770f3d8726c8feda01a5ffb5016b

elements/ntp/README.md

@@ -0,0 +1,8 @@
+Setup ntpd and optionally configure it using Heat metadata.
+
+Heat Metadata can be used to specify the configuration:
+
+    ntp:
+      servers:
+        - { server: server1.foo.example }
+        - { server: server2.foo.test, fudge: stratum 0 }

elements/ntp/element-deps

@@ -0,0 +1,2 @@
+os-apply-config
+os-refresh-config

elements/ntp/install.d/50-ntp

@@ -0,0 +1,3 @@
+#!/bin/bash
+# ntpdate is used when the network is brought up to correct any large time skew
+install-packages ntp ntpdate

elements/ntp/os-apply-config/etc/ntp.conf

@@ -0,0 +1,24 @@
+# /etc/ntp.conf, configuration for ntpd; see ntp.conf(5) for help
+
+driftfile /var/lib/ntp/ntp.drift
+
+# Enable this if you want statistics to be logged.
+#statsdir /var/log/ntpstats/
+
+statistics loopstats peerstats clockstats
+filegen loopstats file loopstats type day enable
+filegen peerstats file peerstats type day enable
+filegen clockstats file clockstats type day enable
+
+# By default, exchange time with everybody, but don't allow configuration.
+restrict -4 default kod notrap nomodify nopeer noquery
+restrict -6 default kod notrap nomodify nopeer noquery
+
+# Local users get more
+restrict 127.0.0.1
+restrict ::1
+
+{{#ntp.servers}}
+server {{server}}
+{{#fudge}}fudge {{server}} {{fudge}}{{/fudge}}
+{{/ntp.servers}}

elements/ntp/os-refresh-config/post-configure.d/50-ntp

@@ -0,0 +1,2 @@
+#!/bin/sh
+service ntp restart || service ntpd restart