cgroups: refine classify_by_rules() function
cgroups: refine classify_by_rules() function

This change makes classify_by_rules() function a bit more human readable
without changing its implementation.

Reviewed-by: Antti-Ville Jansson <f82edea093ea176131f2d7c1890e1559dc4619c9@digia.com>

jusa/ohm-plugins-misc,tswindell/ohm-plugins-misc,maemo-foss/maemo-multimedia-ohm-plugins-misc,jusa/ohm-plugins-misc,jusa/ohm-plugins-misc,tswindell/ohm-plugins-misc,tswindell/ohm-plugins-misc,jusa/ohm-plugins-misc,maemo-foss/maemo-multimedia-ohm-plugins-misc,maemo-foss/maemo-multimedia-ohm-plugins-misc