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.

BOOST_CHECK(result28);
                if (EqualResult(*result27, *result28))
                    fails++;
            }
            BOOST_CHECK_NE(fails, RANDOM_REPEATS);
        }
        
        
        
        add_coin(available_coins, *wallet, 5 * CENT);
        add_coin(available_coins, *wallet, 10 * CENT);
        add_coin(available_coins, *wallet, 15 * CENT);
        add_coin(available_coins, *wallet, 20 * CENT);
        add_coin(available_coins, *wallet, 25 * CENT);
        for (int i = 0; i < RUN_TESTS; i++) {
            int fails = 0;
            for (int j = 0; j < RANDOM_REPEATS; j++)
            {
                const auto result29 = KnapsackSolver(GroupCoins(available_coins.All()), 90 * CENT, CENT);
                BOOST_CHECK(result29);
                const auto result30 = KnapsackSolver(GroupCoins(available_coins.All()), 90 * CENT, CENT);
                BOOST_CHECK(result30);
                if (EqualResult(*result29, *result30))
                    fails++;
            }
            BOOST_CHECK_NE(fails, RANDOM_REPEATS);
        }
    }
}
BOOST_AUTO_TEST_CASE(ApproximateBestSubset)