* ar: refactor network bridge config to use go-cni lib
* ar: use eth as the iface prefix for bridged network namespaces
* vendor: update containerd/go-cni package
* ar: update network hook to use TODO contexts when calling configurator
* unnecessary conversion
Adds a new Prerun and Postrun hooks to manage set up of network namespaces
on linux. Work still needs to be done to make the code platform agnostic and
support Docker style network initalization.
