While regtesting with [bitcoin-spock](https://github.com/msgilligan/bitcoin-spock) I noticed at some point the transaction creation via `sendtoaddress -> CreateTransaction()` fails, because the created transaction is larger than `MAX_STANDARD_TX_SIZE`.

During the process a lot of raw transactions are created, which have smallish outputs and when then using `sendtoaddress`, it appears to attempt to create a transaction that spends too many of those dust-ish outputs.

The transaction to create does not have many outputs, but it looks like it's caused by the coin selection, which selects too many inputs. Testing was done with a 0.9 branch, but on the first glimpse I believe this issue is as well be present in 0.10. If this is a known issue, and if there is already a guard against this behavior, I'd be happy about a hint.

Sorry in advance, I do not have a test script to reproduce this issue in an isolated manner. A potential fix would probably require to adjust the coin selection, so that it selects a combination of coins, which, in addition to the size of the rest of the transaction, is still smaller than the limit.

std::vector<CRecipient> vecSend;
    
    for (size_t idx = 0; idx < tx.vout.size(); idx++) {
        const CTxOut& txOut = tx.vout[idx];
        CRecipient recipient = {txOut.scriptPubKey, txOut.nValue, setSubtractFeeFromOutputs.count(idx) == 1};
        vecSend.push_back(recipient);
    }
    
    
    LOCK(wallet.cs_wallet);
    
    
    std::map<COutPoint, Coin> coins;
    for (const CTxIn& txin : tx.vin) {
        coins[txin.prevout]; 
    }
    wallet.chain().findCoins(coins);
    for (const CTxIn& txin : tx.vin) {
        const auto& outPoint = txin.prevout;
        if (wallet.IsMine(outPoint)) {
            
            coinControl.Select(outPoint);
        } else if (coins[outPoint].out.IsNull()) {
            error = _("Unable to find UTXO for external input");
            return false;
        } else {
            
            coinControl.SelectExternal(outPoint, coins[outPoint].out);
        }
    }