gpo: Improve debug messages
    
    Improve debug messages during security filtering. It was not possible
    to figure out why the GPO was filtered by reading the logs, because
    we use the same debug message in various cases.
    
    Reviewed-by: Lukáš Slebodník <lslebodn@redhat.com>
    (cherry picked from commit 47680083e7e4bf5c433657171bf84cceacc83339)