swarm: nodes not starting correctly

[acud]

We are increasingly noticing a condition in which nodes are not started correctly. This sometimes manifests on the clusters we deploy on k8s, but also on our test suite on travis. It seems that the nodes do not respond and on k8s the nodes in the cluster do not even reply to swarm print-keys. This problem seems to be a regression from v0.5.2 and further investigation is needed to identify and isolate the problem.