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(result1);
        BOOST_CHECK_EQUAL(result1->GetSelectedValue(), 1 * CENT);
        add_coin(available_coins, *wallet, 2*CENT);           
        
        BOOST_CHECK(!KnapsackSolver(KnapsackGroupOutputs(available_coins.All(), *wallet, filter_standard), 3 * CENT, CENT));
        
        const auto result2 = KnapsackSolver(KnapsackGroupOutputs(available_coins.All(), *wallet, filter_confirmed), 3 * CENT, CENT);
        BOOST_CHECK(result2);
        BOOST_CHECK_EQUAL(result2->GetSelectedValue(), 3 * CENT);
        add_coin(available_coins, *wallet, 5*CENT);           
        add_coin(available_coins, *wallet, 10*CENT, CFeeRate(0), 3, true); 
        add_coin(available_coins, *wallet, 20*CENT);          
        
        
        BOOST_CHECK(!KnapsackSolver(KnapsackGroupOutputs(available_coins.All(), *wallet, filter_standard), 38 * CENT, CENT));
        
        BOOST_CHECK(!KnapsackSolver(KnapsackGroupOutputs(available_coins.All(), *wallet, filter_standard_extra), 38 * CENT, CENT));
        
        const auto result3 = KnapsackSolver(KnapsackGroupOutputs(available_coins.All(), *wallet, filter_standard), 37 * CENT, CENT);
        BOOST_CHECK(result3);
        BOOST_CHECK_EQUAL(result3->GetSelectedValue(), 37 * CENT);
        
        const auto result4 = KnapsackSolver(KnapsackGroupOutputs(available_coins.All(), *wallet, filter_confirmed), 38 * CENT, CENT);
        BOOST_CHECK(result4);
        BOOST_CHECK_EQUAL(result4->GetSelectedValue(), 38 * CENT);
        
        const auto result5 = KnapsackSolver(KnapsackGroupOutputs(available_coins.All(), *wallet, filter_confirmed), 34 * CENT, CENT);
        BOOST_CHECK(result5);
        BOOST_CHECK_EQUAL(result5->GetSelectedValue(), 35 * CENT);       
        BOOST_CHECK_EQUAL(result5->GetInputSet().size(), 3U);