Lowering max_connections to 10 prevented the test system itself from
connecting to it. The replication slaves count towards max_connections and
with up to 15 connections in the test, the limit should be higher.
To avouid failures caused by default MariaDB configuration files
containing entries incompatible with mysqltest, mysqltest is
invoked with the glah --no-defaults, which will cause it *not* to
read any configuration files.
This fixes the problem where an encrypted connection would not be created
even though the option for it was there. Also made it configurable outside
of the constructor to make it easier to use in tests.
