Have simple-init enable network.service

When a glean is running on centos with multiple NICs, it will try to
systemctl enable network.service multiple times for each interface.
Because of systemd magic, it is possible for the systemctl command to
fail in a race condition.

glean shouldn't be enabling network.service during boot in
pre-networking phases (Ib2b618dd975ca44e9c6b0a2c9027642ffc46b9b0).  I
have proposed I8319f1ed6498a9d447950c2b4b34bca59e7b97e4 to remove this
and document the behaviour.

This also bring across suse's version
(I20bffabd333ea290d8712ec2a467f2b2d5678f3a)

Change-Id: I89d9443cb61e287bd0d9da3f48315272218ee335
Signed-off-by: Paul Belanger <pabelanger@redhat.com>

diskimage_builder/elements/simple-init/element-deps

@@ -1,4 +1,5 @@
 cloud-init-datasources
+dib-init-system
 install-types
 pip-and-virtualenv
 runtime-ssh-host-keys

diskimage_builder/elements/simple-init/post-install.d/80-simple-init

@@ -0,0 +1,37 @@
+#!/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} =~ (centos|rhel7|fedora) ]]; then
+            # NOTE(pabelanger): Glean requires network.service for
+            # these platforms.
+            systemctl enable network.service
+        elif [[ ${DISTRO_NAME} =~ (opensuse) ]]; then
+            # on suse, this is named wicked.service, but it's the same
+            # as network.service.
+            systemctl enable wicked.service
+        fi
+        ;;
+    openrc)
+        # let dib-init-system's postinstall handle enabling init scripts
+        exit 0
+        ;;
+    sysv)
+        # nothing to do
+        exit 0
+        ;;
+    *)
+        echo "Unsupported init system $DIB_INIT_SYSTEM"
+        exit 1
+        ;;
+esac