Fixing the trade orders to not repeat the amount.

Was seeing text "You created an order to sell 2,000 XRP for 2,000 XRP" when I was expecting "You created an order to sell 10 USD for 2,000 XRP". 

See: [WC-1680](https://ripplelabs.atlassian.net/browse/WC-1680) Orders in the Transaction History are incorrect