Deadlock on simultaneous nodeup

I'm having an issue similar to #60, reproducible very often when I bring up containers with the app at roughly the same time. Looks like each node is waiting for another one, and they're perpetually stuck in `:syncing` state. Here are the `:sys.get_status(Swarm.Tracer)` results from my 5 nodes: https://pastebin.com/EYLg6YNE . No custom options set, all default; clustering with `libcluster` gossip strategy.