fix downloader will not be conitnue (#17761)

if already has started six data task, then start 7th task will suspend, it will not be run

Author: Eric Zhong

cocos/platform/android/java/src/org/cocos2dx/lib/Cocos2dxDownloader.java

@@ -62,6 +62,12 @@ public void onSuccess(int i, Header[] headers, byte[] binaryData) {
         LogD("onSuccess(i:" + i + " headers:" + headers);
         _downloader.onFinish(_id, 0, null, binaryData);
     }
+    
+    @Override
+    public void onFinish() {
+        // onFinish called after onSuccess/onFailure
+        _downloader.runNextTaskIfExists();
+    }
 }
 
 class HeadTaskHandler extends AsyncHttpResponseHandler {
@@ -97,6 +103,12 @@ public void onSuccess(int statusCode, Header[] headers, byte[] responseBody) {
         Cocos2dxDownloader.setResumingSupport(_host, acceptRanges);
         Cocos2dxDownloader.createTask(_downloader, _id, _url, _path);
     }
+    
+    @Override
+    public void onFinish() {
+        // onFinish called after onSuccess/onFailure
+        _downloader.runNextTaskIfExists();
+    }
 
     @Override
     public void onFailure(int statusCode, Header[] headers, byte[] responseBody, Throwable throwable) {