SST scripts should check all server groups in configuration files

SST scripts should check all server groups in configuration files - this task is a split of MENT-1183 for CS editions

Problem

The MariaDB Backup SST script (wsrep_sst_mariabackup) for Galera manually reads options from configuration files using the tool my_print_defaults. However, in a few places, the script only checks the [mysqld] group in the configuration files. For completeness, it should check all server groups read by the mariadbd process.

The full list of server groups is:

• [client-server]
• [server]
• [mysqld]
• [mysqld-X.Y]
• [mariadb]
• [mariadb-X.Y]
• [mariadbd]
• [mariadbd-X.Y]
• [galera]

See here for some more details: https://mariadb.com/kb/en/configuring-mariadb-with-option-files/#server-option-groups