message: tests: Use SelectCoinsBnB directly instead of AttemptSelection
  Instead of calling AttemptSelection with the hopes/instruction that it
  uses BnB, call SelectCoinsBnB directly to test it.
diff: @@ -279,14 +279,14 @@ BOOST_AUTO_TEST_CASE(bnb_search_test)
  empty_wallet();
  add_coin(1);
  vCoins.at(0).nInputBytes = 40; // Make sure that it has a negative effective value. The next check should assert if this somehow got through. Otherwise it will fail
  - BOOST_CHECK(!testWallet.AttemptSelection( 1 * CENT, filter_standard, vCoins, setCoinsRet, nValueRet, coin_selection_params_bnb));
  + BOOST_CHECK(!SelectCoinsBnB(GroupCoins(vCoins), 1 * CENT, coin_selection_params_bnb.m_cost_of_change, setCoinsRet, nValueRet));
  // Test fees subtracted from output:
  empty_wallet();
  add_coin(1 * CENT);
  vCoins.at(0).nInputBytes = 40;
  coin_selection_params_bnb.m_subtract_fee_outputs = true;
  - BOOST_CHECK(testWallet.AttemptSelection( 1 * CENT, filter_standard, vCoins, setCoinsRet, nValueRet, coin_selection_params_bnb));
  + BOOST_CHECK(SelectCoinsBnB(GroupCoins(vCoins), 1 * CENT, coin_selection_params_bnb.m_cost_of_change, setCoinsRet, nValueRet));
  BOOST_CHECK_EQUAL(nValueRet, 1 * CENT);
  // Make sure that can use BnB when there are preset inputs
  