[#11123] Add '/api' explicitly

Author: donghun-cho

web/src/main/java/com/navercorp/pinpoint/web/websocket/ActiveThreadCountHandler.java

@@ -38,7 +38,7 @@
 public abstract class ActiveThreadCountHandler extends TextWebSocketHandler implements PinpointWebSocketHandler {
 
     public static final String APPLICATION_NAME_KEY = "applicationName";
-    public static final String DEFAULT_REQUEST_MAPPING = "/agent/activeThread";
+    public static final String DEFAULT_REQUEST_MAPPING = "/api/agent/activeThread";
 
     static final String API_ACTIVE_THREAD_COUNT = "activeThreadCount";