Also update filter rules if there is a custom filter installed.

This is relevant if the custom filter passes through some categories to
the previous one (which might be the default one). In this case changes
to the filter rules never took effect.

Change-Id: I1a3ab569857d43621ce5df4e690c6e64e6bc7a66
Reviewed-by: Kai Koehne <kai.koehne@qt.io>

src/corelib/io/qloggingregistry.cpp

@@ -359,9 +359,6 @@ void QLoggingRegistry::setApiRules(const QString &content)
 */
 void QLoggingRegistry::updateRules()
 {
-    if (categoryFilter != defaultCategoryFilter)
-        return;
-
     rules = qtConfigRules + configRules + apiRules + envRules;
 
     foreach (QLoggingCategory *cat, categories.keys())