Swarm deadlock repro

This repository serves as a repro for bitwalker/swarm#91 . To start reproducing, simply run:

docker-compose up --scale repro=5

This command will build a docker image with the compiled repro Elixir application, and run 5 instances of the image. All the application does is start Swarm and Libcluster with Cluster.Strategy.Gossip topology. A single process on each node prints state of the local Swarm.Tracker process.