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 <addrman.h>
#include <banman.h>
#include <blockfilter.h>
#include <chain.h>
#include <chainparams.h>
#include <consensusamount.h>
#include <deploymentstatus.h>
#include <fs.h>
#include <hash.h>
#include <httprpc.h>
#include <httpserver.h>
#include <indexblockfilterindex.h>
#include <indexcoinstatsindex.h>
#include <indextxindex.h>
#include <initcommon.h>
#include <interfaceschain.h>
#include <interfacesinit.h>
#include <interfacesnode.h>
#include <mapport.h>
#include <net.h>
#include <net_permissions.h>
#include <net_processing.h>
#include <netbase.h>
#include <netgroup.h>
#include <nodeblockstorage.h>
#include <nodecaches.h>
#include <nodechainstate.h>
#include <nodechainstatemanager_args.h>
#include <nodecontext.h>
#include <nodeinterface_ui.h>