Plugin to add IP address to dummy interface

[mdgreenfield]

We have a use case where we'd like to add IP 169.254.169.254 (the same IP used by cloud provider Metadata Services) to the network namespace of a container for an application running to bind to (i.e. we're running a fake Metadata Service as an injected sidecar).

I have developed a more generic plugin to do this which creates a dummy interface in the container's network namespace and then adds any configured IPs.

Per the CONTRIBUTING docs, if this is something that seems to fit with this repo I'd be happy to open a PR with that plugin.