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/Dockerfile

@@ -23,6 +23,7 @@ RUN cp bin/containerd bin/ctr bin/containerd-shim /usr/bin/
 ADD cmd /go/src/cmd
 RUN cd /go/src/cmd/service && ./skanky-vendor.sh $GOPATH/src/github.com/containerd/containerd
 RUN go-compile.sh /go/src/cmd/service
+RUN mkdir -p /etc/init.d && ln -s /usr/bin/service /etc/init.d/020-containerd
 
 WORKDIR /
 COPY . .
@@ -33,4 +34,5 @@ WORKDIR /
 COPY --from=alpine /usr/bin/containerd /usr/bin/ctr /usr/bin/containerd-shim /go/bin/service /usr/bin/
 COPY --from=alpine /etc/containerd/config.toml /etc/containerd/
 COPY --from=alpine /usr/share/zoneinfo/UTC /etc/localtime
+COPY --from=alpine /etc/init.d/ /etc/init.d/
 COPY etc etc/