[FIX] return balance from main account

return only the balance from main account.

calculation confuses users
```
2014-02-16 16:22:02 - ERROR -->  Wallet does not cover AP payouts - Payout: 1064.95853252 - Balance: -40,000
```
tested with 2 accounts in wallet, default account has funds of 40,000 and second account has 80,000. so there are liquid funds of 40,000 coins, but substracting 80,000 from main account makes the balance negative and payouts fail. better to return only the balance from default account without substracting the funds from other accounts. doesn't matter if there are funds in other accounts, when liquid funds in default account are enough to payout users.