Fix warning on MySQL >=5.5

I always got this warning for every mysql command I do:

```
Warning: Using unique option prefix pass instead of password is deprecated 
and will be removed in a future release. Please use the full name instead.
```

[example](http://www.serveridol.com/2013/11/19/mysql-dump-warning-using-unique-option-prefix-pass-instead-of-password-is-deprecated/)

I don't know when this password option was introduced, so it might break on earlier versions of MySQL.