fix the spring mvc plugin occur exception when the application runnin…

…g with spring 3

apm-sniffer/apm-sdk-plugin/spring-plugins/mvc-annotation-4.x-plugin/src/main/java/org/skywalking/apm/plugin/spring/mvc/define/AbstractControllerInstrumentation.java

@@ -111,4 +111,13 @@ protected ClassMatch enhanceClass() {
     }
 
     protected abstract String[] getEnhanceAnnotations();
+
+    @Override protected String[] witnessClasses() {
+        /**
+         * @see {@link org.springframework.web.servlet.tags.ArgumentTag}
+         */
+        return new String[]{
+            "org.springframework.web.servlet.tags.ArgumentTag"
+        };
+    }
 }