The github.com/containerd/containerd/services/server has a lot of
dependencies, like content, snapshots services implementation and
docker-metrics.
For the client side, it uses the config struct from server package
to start up the containerd in background. It will import a lot of
useless packages which might be conflict with existing vendor's package.
It makes integration easier with single config package.
Signed-off-by: Wei Fu <fuweid89@gmail.com>
