invoke_service_command

# File lib/drb/extservm.rb, line 75
    def invoke_service_command(name, command)
      raise "invalid command. name: #{name}" unless command
      synchronize do
        return if @servers.include?(name)
        @servers[name] = false
      end
      uri = @uri || DRb.uri
      spawn("#{command} #{uri} #{name}")
    end