introduce image-updater

image/overlay/etc/init.d/image-updater

@@ -0,0 +1,12 @@
+#!/sbin/openrc-run
+
+depend() {
+	need docker
+}
+
+supervisor="supervise-daemon"
+restart_max=5
+restart_delay=10
+
+command="/usr/bin/image-updater"
+pidfile="/run/${RC_SVCNAME}.pid"