Execute a function through the master network interface.

def master_call(self, **kwargs):
        '''
        Execute a function through the master network interface.
        '''
        load = kwargs
        load['cmd'] = self.client
        channel = salt.transport.client.ReqChannel.factory(self.opts,
                                                           crypt='clear',
                                                           usage='master_call')
        try:
            ret = channel.send(load)
        finally:
            channel.close()
        if isinstance(ret, collections.Mapping):
            if 'error' in ret:
                salt.utils.error.raise_error(**ret['error'])
        return ret