mariadb: install config files readable for all

Until now $(INSTALL_CONF) is used for configuration files that go into
/etc/mysql. This commit replaces that with $(INSTALL_DATA). The
configuration files are not only parsed by the server, but also by the
clients (which can be anybody).

This also removes a comment about a cron job from one of the
configuration files. There is no cron job.

Signed-off-by: Sebastian Kemper <sebastian_ml@gmx.net>

utils/mariadb/conf/50-server.cnf

@@ -56,7 +56,6 @@ query_cache_size	= 16M
 #
 # * Logging and Replication
 #
-# Both location gets rotated by the cronjob.
 # Be aware that this log type is a performance killer.
 # As of 5.1 you can enable the log at runtime!
 #general_log_file	= /var/log/mysql/mysql.log