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.

const auto result6 = KnapsackSolver(KnapsackGroupOutputs(available_coins.All(), *wallet, filter_confirmed), 7 * CENT, CENT);
        BOOST_CHECK(result6);
        BOOST_CHECK_EQUAL(result6->GetSelectedValue(), 7 * CENT);
        BOOST_CHECK_EQUAL(result6->GetInputSet().size(), 2U);
        
        const auto result7 = KnapsackSolver(KnapsackGroupOutputs(available_coins.All(), *wallet, filter_confirmed), 8 * CENT, CENT);
        BOOST_CHECK(result7);
        BOOST_CHECK(result7->GetSelectedValue() == 8 * CENT);
        BOOST_CHECK_EQUAL(result7->GetInputSet().size(), 3U);
        
        const auto result8 = KnapsackSolver(KnapsackGroupOutputs(available_coins.All(), *wallet, filter_confirmed), 9 * CENT, CENT);
        BOOST_CHECK(result8);
        BOOST_CHECK_EQUAL(result8->GetSelectedValue(), 10 * CENT);
        BOOST_CHECK_EQUAL(result8->GetInputSet().size(), 1U);
        
        available_coins.Clear();
        add_coin(available_coins, *wallet,  6*CENT);
        add_coin(available_coins, *wallet,  7*CENT);
        add_coin(available_coins, *wallet,  8*CENT);
        add_coin(available_coins, *wallet, 20*CENT);
        add_coin(available_coins, *wallet, 30*CENT); 
        
        const auto result9 = KnapsackSolver(KnapsackGroupOutputs(available_coins.All(), *wallet, filter_confirmed), 71 * CENT, CENT);
        BOOST_CHECK(result9);
        BOOST_CHECK(!KnapsackSolver(KnapsackGroupOutputs(available_coins.All(), *wallet, filter_confirmed), 72 * CENT, CENT));
        
        const auto result10 = KnapsackSolver(KnapsackGroupOutputs(available_coins.All(), *wallet, filter_confirmed), 16 * CENT, CENT);
        BOOST_CHECK(result10);
        BOOST_CHECK_EQUAL(result10->GetSelectedValue(), 20 * CENT);