If one calls `fundrawtransaction`, the change address will be retrieved from the keypool, though, this key/address will always be returned to the pool, leading to the problem that the next `getnewaddress()` call will restult in the same key/address.

Either we remove the auto-change-address (users would need to call `getrawchangeaddress` first [current best practice anyway]) or we add a call to keep/mark a specific key/address as change (after one have sent the funded raw transaction).

Reported by @NicolasDorier on IRC.
{
    return pwalletMain && pwalletMain->IsCrypted()
        ? "\nRequires wallet passphrase to be set with walletpassphrase call."
        : "";
}
bool EnsureWalletIsAvailable(bool avoidException)
{
    if (!pwalletMain)
    {
        if (!avoidException)
            throw JSONRPCError(RPC_METHOD_NOT_FOUND, "Method not found (disabled)");
        else
            return false;
    }
    return true;
}
void EnsureWalletIsUnlocked()