Fix: inverted logic in loglevel_parse_range_string_common function

Fix: inverted logic in loglevel_parse_range_string_common function

The mapping of numerical severity levels to their corresponding names
varies across different logging domains. Some domains, like
Java Util Logging, use higher numerical values for more severe logging
levels, while others, like Log4j2, use lower values for the same
purpose.

To accommodate this variation, the `loglevel_parse_range_string_common`
function has been updated. It now accepts the numerical value
representing the most severe logging level in a given domain. This
change ensures that log level specifications in the format `TRACE..` are
parsed correctly, regardless of the domain's convention.

Change-Id: Idbc3949ac33b69c71fce484a6d8912f59cdbe08d
Signed-off-by: Michael Jeanson <mjeanson@efficios.com>
Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>