salvagewallet drops valid keys

Need to look into this next week but I will disable the check in travis in the meantime.

``` python
check -salvagewallet
Assertion failed: [Decimal('33.99911140'), Decimal('5549.99796160'), Decimal('65.99974900')] != [Decimal('0E-8'), Decimal('5549.99796160'), Decimal('65.99974900')]
```

Edit: Will submit a proper fix tomorrow...
