Currently the rkt driver does not expose a DriverNetwork instance after
starting the container, which means that address_mode = 'driver' does
not work.

To get the container network information, we can call `rkt status` on
the UUID of the container and grab the container IP from there.

For the port map, we need to grab the pod manifest as it will tell us
which ports the container exposes. We then cross-reference the
configured port name with the container port names, and use that to
create a correct port mapping.

To avoid doing a (bad) reimplementation of the appc schema(which rkt
uses for its manifest) and rkt apis, we pull those in as vendored
dependencies. The versions used are the same ones that rkt use in their
glide dependency configuration for version 1.28.0.