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.
GetMainSignals().FlushBackgroundCallbacks();
    
    if (g_txindex) {
        g_txindex->Stop();
        g_txindex.reset();
    }
    if (g_coin_stats_index) {
        g_coin_stats_index->Stop();
        g_coin_stats_index.reset();
    }
    ForEachBlockFilterIndex([](BlockFilterIndex& index) { index.Stop(); });
    DestroyAllBlockFilterIndexes();
    
    
    
    
    
    if (node.chainman) {
        LOCK(cs_main);
        for (Chainstate* chainstate : node.chainman->GetAll()) {
            if (chainstate->CanFlushToDisk()) {
                chainstate->ForceFlushStateToDisk();
                chainstate->ResetCoinsViews();
            }
        }
    }
    for (const auto& client : node.chain_clients) {
        client->stop();
    }
#if ENABLE_ZMQ