refactor(性能测试): 避免重复添加 backend listener

--bug=1011512 --user=刘瑞斌 【性能测试】有一个性能测试一直在running，应是已经跑完了 https://www.tapd.cn/55049933/s/1124218

backend/src/main/java/io/metersphere/performance/engine/EngineContext.java

@@ -16,6 +16,7 @@ public class EngineContext {
     private Map<String, Object> properties = new HashMap<>();
     private Map<String, byte[]> testResourceFiles = new HashMap<>();
     private Map<String, Boolean> splitFlag = new HashMap<>();
+    private boolean checkBackendListener;
 
     public String getTestId() {
         return testId;
@@ -117,4 +118,12 @@ public class EngineContext {
     public void setSplitFlag(Map<String, Boolean> splitFlag) {
         this.splitFlag = splitFlag;
     }
+
+    public boolean isCheckBackendListener() {
+        return checkBackendListener;
+    }
+
+    public void setCheckBackendListener(boolean checkBackendListener) {
+        this.checkBackendListener = checkBackendListener;
+    }
 }

backend/src/main/java/io/metersphere/performance/parse/xml/reader/JmeterDocumentParser.java

@@ -612,6 +612,10 @@ public class JmeterDocumentParser implements EngineSourceParser {
         if (checkLicense() && !BooleanUtils.toBoolean(resourcePool.getBackendListener())) {
             return;
         }
+        // 已经添加过不再重复添加
+        if (context.isCheckBackendListener()) {
+            return;
+        }
 
         Element listenerParent = getNextSibling(element);
 
@@ -632,6 +636,8 @@ public class JmeterDocumentParser implements EngineSourceParser {
         backendListener.addAttribute("enabled", "true");
 
         listenerParent.addElement(HASH_TREE_ELEMENT);
+        // 标记已经添加上
+        context.setCheckBackendListener(true);
     }
 
     private boolean checkLicense() {