Switch runc and containerd startup to be entirely Go

At present they use a small shared function called "prepare"
that does the read-write remounts, that I will switch to doing overlay
mounts soon.

Signed-off-by: Justin Cormack <justin.cormack@docker.com>

pkg/containerd/etc/init.d/020-containerd

@@ -1,14 +0,0 @@
-#!/bin/sh
-
-# start service containers
-
-if [ -d /containers/services ]
-then
-	for f in $(find /containers/services -mindepth 1 -maxdepth 1 | sort)
-	do
-		/bin/mount --bind "$f/rootfs" "$f/rootfs"
-		mount -o remount,rw "$f/rootfs"
-	done
-fi
-
-service system-init