key-sync fails when node.network.interface hashes do not contain addresses

[nephomaniac]

self.get_local_cluster_name() in key-sync.rb needs to verify that parameters are present, and/or not nil before attempting to iterate on the contents. For example, the following will fail when run on a machine where the interface does not posses 'addresses', resulting in a nil value which you can not iterate on here...

node["network"]["interfaces"].each do |interface, info|
    info["addresses"].each do |address, info|