Always show MySQL variables, also if check is ok

[eldering]

This helps quickly inspecting settings, in my case for example the MySQL transaction isolation level.
We should probably do this for all configuration settings.

[meisterT]

I would write these to reduce duplication:

$desc .= sprintf("max_connections is set to %s.\n", $vars['max_connections']);
if ($vars['max_connections'] < 300) {
            $result = 'W';
            $desc .= sprintf("In our experience you need at least 300, but better 1000 connections to prevent connection refusal during the contest.\n", $vars['max_connections']);
}