Fix [WorldGuard] in log messages stacking on reloads.

Fixes WORLDGUARD-3192.

src/main/java/com/sk89q/worldguard/util/logging/RecordMessagePrefixer.java

@@ -62,9 +62,12 @@ public void close() throws SecurityException {
     public static void register(Logger logger, String prefix) {
         checkNotNull(logger);
 
+        // Fix issues with multiple classloaders loading the same class
+        String className = RecordMessagePrefixer.class.getCanonicalName();
+
         logger.setUseParentHandlers(false);
         for (Handler handler : logger.getHandlers()) {
-            if (handler instanceof RecordMessagePrefixer) {
+            if (handler.getClass().getCanonicalName().equals(className)) {
                 logger.removeHandler(handler);
             }
         }