fetch_kddcup99 does not shuffle data

code snipet to reproduce:
```py
from sklearn.datasets import fetch_kddcup99
dataset = fetch_kddcup99(subset='SA', shuffle=True, percent10=True)
assert(all(dataset.target[-100:] != 'normal.'))
assert(all(dataset.target[:100] == 'normal.'))
```

That is because shuffling should be done in `fetch_kddcup99` not in `_fetch_brute_kddcup99`. 
