MySQL verification fails - unable to start server

When trying to verify a MySQL backup:

```
sh-5.0$ ./backup.sh -v mariadb=matomo-db:3306/matomo

Verifying backup ...

Settings:
- Database: mariadb=matomo-db:3306/matomo
- Backup file: /backups/daily/2021-07-27/matomo-db-matomo_2021-07-27_05-40-37.sql.gz

Would you like to continue? Press Ctrl-C to exit, or any other key to continue ...

Cleaning up ...

waiting for server to start..............................................................................................................................................................................................................................................................................................................................................................
The server failed to start within 0h:6m:0s.

The server started in 0h:6m:0s.

Warning: World-writable config file '/etc/my.cnf.d/40-paas.cnf' is ignored
Warning: World-writable config file '/etc/my.cnf.d/50-my-tuning.cnf' is ignored
Warning: World-writable config file '/etc/my.cnf.d/base.cnf' is ignored
mysqladmin: connect to server at 'localhost' failed
error: 'Can't connect to local MySQL server through socket '/var/lib/mysql/mysql.sock' (2)'
Check that mysqld is running and that the socket: '/var/lib/mysql/mysql.sock' exists!
Already clean ...

[!!ERROR!!] - Backup verification failed: /backups/daily/2021-07-27/matomo-db-matomo_2021-07-27_05-40-37.sql.gz

Elapsed time: 0h:6m:0s - Status Code: 1
```

This used to work at the time of the release, so it might be a change in the underlying MySQL image.