Fix interface for brandao2013mvp algorithm

```
  File "/opt/container-balancer-controller/balance/problem.py", line 48, in solve
    return pack_vectors(problem=self._to_algo_problem(), family='brandao2013mvp')
  File "/usr/local/lib/python3.4/dist-packages/vectorpack/__init__.py", line 31, in pack_vectors
    result = module.pack_vectors(problem, **kwargs)
TypeError: pack_vectors() takes 0 positional arguments but 1 was given
```