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.
{
    return m_network == CBaseChainParams::MAIN || m_network_only_args.count(arg) == 0;
}
util::SettingsValue ArgsManager::GetSetting(const std::string& arg) const
{
    LOCK(cs_args);
    return util::GetSetting(
        m_settings, m_network, SettingName(arg), !UseDefaultSection(arg),
        false, false);
}
std::vector<util::SettingsValue> ArgsManager::GetSettingsList(const std::string& arg) const
{
    LOCK(cs_args);
    return util::GetSettingsList(m_settings, m_network, SettingName(arg), !UseDefaultSection(arg));
}
void ArgsManager::logArgsPrefix(