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.
using kernel::ValidationCacheSizes;
using node::ApplyArgsManOptions;
using node::CacheSizes;
using node::CalculateCacheSizes;
using node::DEFAULT_PERSIST_MEMPOOL;
using node::DEFAULT_PRINTPRIORITY;
using node::DEFAULT_STOPAFTERBLOCKIMPORT;
using node::LoadChainstate;
using node::MempoolPath;
using node::ShouldPersistMempool;
using node::NodeContext;
using node::ThreadImport;
using node::VerifyLoadedChainstate;
using node::fPruneMode;
using node::fReindex;
using node::nPruneTarget;
static constexpr bool DEFAULT_PROXYRANDOMIZE{true};
static constexpr bool DEFAULT_REST_ENABLE{false};
static constexpr bool DEFAULT_I2P_ACCEPT_INCOMING{true};
#ifdef WIN32
#define MIN_CORE_FILEDESCRIPTORS 0
#else
#define MIN_CORE_FILEDESCRIPTORS 150
#endif
static const char* DEFAULT_ASMAP_FILENAME="ip_asn.map";
**
 * The PID file facilities.
 *
static const char* BITCOIN_PID_FILENAME = "bitcoind.pid";
static fs::path GetPidFile(const ArgsManager& args)