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.
"from a different location, it will be unable to locate the current data files. There could "
                  "also be data loss if bitcoin is started while in a temporary directory.\n",
                  args.GetArg("-datadir", ""), fs::PathToString(fs::current_path()));
    }
    ValidationCacheSizes validation_cache_sizes{};
    ApplyArgsManOptions(args, validation_cache_sizes);
    if (!InitSignatureCache(validation_cache_sizes.signature_cache_bytes)
        || !InitScriptExecutionCache(validation_cache_sizes.script_execution_cache_bytes))
    {
        return InitError(strprintf(_("Unable to allocate memory for -maxsigcachesize: '%s' MiB"), args.GetIntArg("-maxsigcachesize", DEFAULT_MAX_SIG_CACHE_BYTES >> 20)));
    }
    int script_threads = args.GetIntArg("-par", DEFAULT_SCRIPTCHECK_THREADS);
    if (script_threads <= 0) {
        
        
        script_threads += GetNumCores();
    }
    
    script_threads = std::max(script_threads - 1, 0);
    
    script_threads = std::min(script_threads, MAX_SCRIPTCHECK_THREADS);
    LogPrintf("Script verification uses %d additional threads\n", script_threads);
    if (script_threads >= 1) {
        StartScriptCheckWorkerThreads(script_threads);
    }
    assert(!node.scheduler);
    node.scheduler = std::make_unique<CScheduler>();
    
    node.scheduler->m_service_thread = std::thread(util::TraceThread, "scheduler", [&] { node.scheduler->serviceQueue(); });