CORE-524: Respect HTTP response codes.
CORE-524: Respect HTTP response codes.

This removes the special logic in the `createTransaction()` function to convert an 'error' (not 200) into a 'success' (on 201) - now a 201 is 'success'.

breadwallet/breadwallet-core,breadwallet/breadwallet-core,breadwallet/breadwallet-core,breadwallet/breadwallet-core,breadwallet/breadwallet-core,breadwallet/breadwallet-core