def elb_registration_check(type)
      details = retry_elb_fn("describe_load_balancers",@elb_name)
      instances = details.first[:instances]
      case type
      when :all
        @servers.each do |server|
          server.settings
          aws_id = server["aws-id"]
          raise "ERROR: Did not find aws id for #{aws_id}. ID list: #{instances.inspect}" unless instances.include?(aws_id)
        end
      when :none
        raise "ERROR: found registered instances when there should be none. ID list: #{instances.inspect}" unless instances.empty?
      else
        raise "ERROR: only check types of :none and :all are currently supported" 
      end
    end
def elb_registration_check(type)
      details = retry_elb_fn("describe_load_balancers",@elb_name)
      instances = details.first[:instances]
      case type
      when :all
        @servers.each do |server|
          server.settings
          aws_id = server["aws-id"]
          raise "ERROR: Did not find aws id for #{aws_id}. ID list: #{instances.inspect}" unless instances.include?(aws_id)
        end
      when :none
        raise "ERROR: found registered instances when there should be none. ID list: #{instances.inspect}" unless instances.empty?
      else
        raise "ERROR: only check types of :none and :all are currently supported" 
      end
    end
Check if :all or :none of the app servers are registered