nixos/tests/mariadb-galera-mariabackup: fix test script
nixos/tests/mariadb-galera-mariabackup: fix test script

MariaDB 10.4 introduces a number of changes to the authentication
process, intended to make things easier and more intuitive.

NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs