When downloading and running Bitcoin core for the first time, after clicking through the "Are you sure you want to open. it?" screen, there's a possibility that macOS will pass an argument like `-psn_0_SOME_ID` to the application, which results in a shutdown as it's an invalid argument:

![v0 19 0rc1 args shutdown](https://user-images.githubusercontent.com/863730/67034964-b026fc00-f0e6-11e9-8462-70d0fcf613e6.png)

This only happens on the first run, subsequent opens will work fine, but we should filter these out, otherwise it's a poor and confusing first experience.

found_result = GetArgHelper(am.m_override_args, arg, true);
        if (found_result.first) {
            return found_result;
        }
        
        
        
        if (!am.m_network.empty()) {
            found_result = GetArgHelper(am.m_config_args, NetworkArg(am, arg));
            if (found_result.first) {
                return found_result;
            }
        }
        if (UseDefaultSection(am, arg)) {
            found_result = GetArgHelper(am.m_config_args, arg);
            if (found_result.first) {
                return found_result;
            }
        }
        return found_result;
    }
    /* Special test for -testnet and -regtest args, because we
     * don't want to be confused by craziness like "[regtest] testnet=1"
     */
    static inline bool GetNetBoolArg(const ArgsManager &am, const std::string& net_arg) EXCLUSIVE_LOCKS_REQUIRED(am.cs_args)
    {
        std::pair<bool,std::string> found_result(false,std::string());
        found_result = GetArgHelper(am.m_override_args, net_arg, true);