first docker-driven integration test

adds a docker-driven integration test

**scenario**
* three nodes: `bootstrap`, `server`, `client`

1. boostrap enters network
1. server and client connect
1. server adds randomly generated file (client waits for signal to add file)
1. server sends signal then client adds the file
1. client verifies file
1. all nodes exit

`dhcpcd` does this, established a connection and daemonizes once its all set up.