fix `ConcurrentHashSet` compatibility problems (#5122)

common/src/main/java/com/alibaba/nacos/common/utils/ConcurrentHashSet.java

@@ -17,7 +17,10 @@
 package com.alibaba.nacos.common.utils;
 
 import java.util.AbstractSet;
+import java.util.ArrayList;
 import java.util.Iterator;
+import java.util.List;
+import java.util.Map;
 import java.util.concurrent.ConcurrentHashMap;
 
 /**
@@ -46,7 +49,11 @@ public class ConcurrentHashSet<E> extends AbstractSet<E> {
     
     @Override
     public Iterator<E> iterator() {
-        return map.keySet().iterator();
+        List<E> list = new ArrayList<E>();
+        for (Map.Entry<E, Boolean> entry : map.entrySet()) {
+            list.add(entry.getKey());
+        }
+        return list.iterator();
     }
     
     @Override