EDITED 2019-02-08

`maxTxFee` is a global variable, used by both the raw transaction and wallet RPCs. It's set from `-maxtxfee`.

~listed in the global help text in init.cpp, but is only set in `WalletInit::ParameterInteraction()`. If the wallet is disabled, then `-maxtxfee` is ignored and the default is used.~

~This behaviour has existed since the mempool was changed to limit acceptance based on `maxTxFee` in https://github.com/bitcoin/bitcoin/commit/fa331db68bcc68e4c93fb45aaa30f911b0ecfe1a.~

~Short-term fix is to move the `-maxtxfee` handling to `InitParameterInteraction()` in init.cpp.~
EDIT: `maxTxFee` initiation bug fixed in #15357 

I don't think we should share this setting between the node and wallet.
g_wallet_init_interface.Construct(interfaces);
    /* Register RPC commands regardless of -server setting so they will be
     * available in the GUI RPC console even if external calls are disabled.
     */
    RegisterAllCoreRPCCommands(tableRPC);
    for (const auto& client : interfaces.chain_clients) {
        client->registerRpcs();
    }
    g_rpc_interfaces = &interfaces;
#if ENABLE_ZMQ
    RegisterZMQRPCCommands(tableRPC);
#endif
    /* Start the RPC server already.  It will be started in "warmup" mode
     * and not really process calls already (but it will signify connections
     * that the server is there and will be ready later).  Warmup mode will
     * be disabled when initialisation is finished.
     */
    if (gArgs.GetBoolArg("-server", false))
    {
        uiInterface.InitMessage_connect(SetRPCWarmupStatus);
        if (!AppInitServers())
            return InitError(_("Unable to start HTTP server. See debug log for details."));
    }
    
    for (const auto& client : interfaces.chain_clients) {
        if (!client->verify()) {