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.
{
    node.chain = node.init->makeChain();
    return true;
}
bool AppInitMain(NodeContext& node, interfaces::BlockAndHeaderTipInfo* tip_info)
{
    const ArgsManager& args = *Assert(node.args);
    const CChainParams& chainparams = Params();
    auto opt_max_upload = ParseByteUnits(args.GetArg("-maxuploadtarget", DEFAULT_MAX_UPLOAD_TARGET), ByteUnit::M);
    if (!opt_max_upload) {
        return InitError(strprintf(_("Unable to parse -maxuploadtarget: '%s'"), args.GetArg("-maxuploadtarget", "")));
    }
    
    if (!CreatePidFile(args)) {
        
        return false;
    }
    if (!init::StartLogging(args)) {
        
        return false;
    }
    LogPrintf("Using at most %i automatic connections (%i file descriptors available)\n", nMaxConnections, nFD);
    
    if (args.IsArgSet("-datadir") && !args.GetPathArg("-datadir").is_absolute()) {
        LogPrintf("Warning: relative datadir option '%s' specified, which will be interpreted relative to the " 
                  "current working directory '%s'. This is fragile, because if bitcoin is started in the future "