On my Linux Mint 19.1:
```bash
$ umask
0022
```

After the first run of `bitcoin-qt -sysperm=false` the `0700` permissions are expected for both the datadir (`~/.bitcoin`) and the walletdir (`~/.bitcoin/wallets`).

Actually, the directories are created with such access permissions:
```bash
$ stat ~/.bitcoin | grep Uid
Access: (0755/drwxr-xr-x)  Uid: ( 1000/ hebasto)   Gid: ( 1000/ hebasto)
$ stat ~/.bitcoin/wallets | grep Uid
Access: (0755/drwxr-xr-x)  Uid: ( 1000/ hebasto)   Gid: ( 1000/ hebasto)
```

Refs:
- #4286
- #13371
- #13389

NOTE: reading through the initial PR #4286 makes me think it was controversial. Is it a better and simpler way to just get rid of `-sysperm` option? I believe a user who needs this option can easily run `chown` command.
{
    std::string cmd = args.GetArg("-startupnotify", "");
    if (!cmd.empty()) {
        std::thread t(runCommand, cmd);
        t.detach(); 
    }
}
#endif
static bool AppInitServers(NodeContext& node)
{
    const ArgsManager& args = *Assert(node.args);
    RPCServer::OnStarted(&OnRPCStarted);
    RPCServer::OnStopped(&OnRPCStopped);
    if (!InitHTTPServer())
        return false;
    StartRPC();
    node.rpc_interruption_point = RpcInterruptionPoint;
    if (!StartHTTPRPC(&node))
        return false;
    if (args.GetBoolArg("-rest", DEFAULT_REST_ENABLE)) StartREST(&node);
    StartHTTPServer();
    return true;
}
void InitParameterInteraction(ArgsManager& args)