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.
#include <utilsyserror.h>
#include <utilsystem.h>
#include <utilthread.h>
#include <utilthreadnames.h>
#include <utiltranslation.h>
#include <validation.h>
#include <validationinterface.h>
#include <walletinitinterface.h>
#include <algorithm>
#include <condition_variable>
#include <cstdint>
#include <cstdio>
#include <fstream>
#include <functional>
#include <set>
#include <string>
#include <thread>
#include <vector>
#ifndef WIN32
#include <cerrno>
#include <signal.h>
#include <sysstat.h>
#endif
#include <boostsignals2signal.hpp>
#if ENABLE_ZMQ
#include <zmqzmqabstractnotifier.h>
#include <zmqzmqnotificationinterface.h>
#include <zmqzmqrpc.h>
#endif
using kernel::DumpMempool;