def close_one(identity, propagate = true, &blk)
      broker = @brokers_hash[identity]
      raise Exception, "Cannot close unknown broker #{identity}" unless broker
      broker.close(propagate, &blk)
      true
    end
def close_one(identity, propagate = true, &blk)
      broker = @brokers_hash[identity]
      raise Exception, "Cannot close unknown broker #{identity}" unless broker
      broker.close(propagate, &blk)
      true
    end
Close an individual broker client connection

 === Parameters
 identity(String):: Broker serialized identity
 propagate(Boolean):: Whether to propagate connection status updates

 === Block
 Optional block with no parameters to be called after connection closed

 === Return
 true:: Always return true

 === Raise
 Exception:: If broker unknown