Set quit signal

def quit(self):
        '''Set quit signal'''
        self._quit = True
        # stop xmlrpc server
        if hasattr(self, 'xmlrpc_server'):
            self.xmlrpc_ioloop.add_callback(self.xmlrpc_server.stop)
            self.xmlrpc_ioloop.add_callback(self.xmlrpc_ioloop.stop)