Manage NTP on zuul workers in DIB

Currently, NTP is configured on zuul workers via puppet[1]. As part of
reducing the nodepool image builds' dependency on puppet, this patch
adds the necessary package dependencies and service configuration to
have NTP running on nodes without needing puppet to install and start
it.

[1] http://git.openstack.org/cgit/openstack-infra/system-config/tree/modules/openstack_project/manifests/template.pp?id=1b0e016093a71ad4eb1b4dde55ac9398b2505f24#n243

Change-Id: Iee6babc183dd12cc82ce76ddfde04f2d98ddc4d6

nodepool/elements/infra-package-needs/package-installs.yaml

@@ -6,6 +6,7 @@ python-dev:
 python3-dev:
 uuid-runtime:
 traceroute:
+ntp:
 ntpdate:
 gentoolkit:
 at:

nodepool/elements/infra-package-needs/pkg-map

@@ -6,6 +6,7 @@
     "gentoo": {
       "build-essential": "",
       "cron": "sys-process/cronie",
+      "ntp": "net-misc/ntp",
       "python-dev": "",
       "python3-dev": "",
       "traceroute": "net-analyzer/traceroute",
@@ -18,6 +19,7 @@
       "build-essential": "glibc-devel gcc make",
       "dnsutils": "bind-utils",
       "iputils-ping": "iputils",
+      "ntp": "ntp ntp-perl",
       "python-dev": "python-devel",
       "python3-dev": "",
       "uuid-runtime": ""

nodepool/elements/infra-package-needs/post-install.d/80-enable-infra-services

@@ -0,0 +1,33 @@
+#!/bin/bash
+
+if [ "${DIB_DEBUG_TRACE:-0}" -gt 0 ]; then
+    set -x
+fi
+set -eu
+set -o pipefail
+
+case "$DIB_INIT_SYSTEM" in
+    upstart)
+        # nothing to do
+        exit 0
+        ;;
+    systemd)
+        if [[ $DISTRO_NAME = "ubuntu" || $DISTRO_NAME = "debian" ]]; then
+            systemctl enable ntp.service
+        else
+            systemctl enable ntpd.service
+        fi
+        ;;
+    openrc)
+        # let dib-init-system's postinstall handle enabling init scripts
+        exit 0
+        ;;
+    sysv)
+        # ntp is enabled by default, nothing to do
+        exit 0
+        ;;
+    *)
+        echo "Unsupported init system $DIB_INIT_SYSTEM"
+        exit 1
+        ;;
+esac