I want to avoid that upgrades silently change important config parameters
that users have come to rely on. This could happen if users changed their
my.cnf themselves, and then an upgrade introduces mariadb.cnf which silently
overrides the settings in my.cnf. Avoid this by having mariadb.cnf mostly
empty for now, and in the future we can add just new mariadb-specific
options there that do not break existing installations.