dirty flush only work when open flush (#70)

Co-authored-by: alantong(佟明达) <[email protected]>

src/main/java/org/apache/hadoop/fs/CosNFSDataOutputStream.java

@@ -178,7 +178,10 @@ public synchronized void flush() throws IOException {
 
     private void innerFlush(boolean closeStream) throws IOException {
         this.checkOpened();
-        if (!this.dirty) {
+        // when close flush data to cos, each time data not upload,
+        // at this time if we close stream, it is not dirty but also has data need to upload
+        // so the dirty flag only useful when flush cos enabled.
+        if (!this.dirty && this.flushCOSEnabled) {
             LOG.debug("The stream is up-to-date, no need to refresh.");
             return;
         }