Close the FileChannel in case of an IOException in AbstractDiskHttpData.addContent. (#10188)

Motivation:

`FileChannel.force` may throw an IOException. A fd leak may happen here.

Modification:

Close the fileChannel in a finally block.

Result:

Avoid fd leak.

codec-http/src/main/java/io/netty/handler/codec/http/multipart/AbstractDiskHttpData.java

@@ -182,8 +182,11 @@ public abstract class AbstractDiskHttpData extends AbstractHttpData {
                 RandomAccessFile accessFile = new RandomAccessFile(file, "rw");
                 fileChannel = accessFile.getChannel();
             }
-            fileChannel.force(false);
-            fileChannel.close();
+            try {
+                fileChannel.force(false);
+            } finally {
+                fileChannel.close();
+            }
             fileChannel = null;
             setCompleted();
         } else {

codec-http/src/test/java/io/netty/handler/codec/http/multipart/DiskFileUploadTest.java

@@ -16,11 +16,15 @@
 package io.netty.handler.codec.http.multipart;
 
 import io.netty.buffer.Unpooled;
+import io.netty.util.CharsetUtil;
+
 import org.junit.Test;
 
 import java.io.File;
+import java.io.FileInputStream;
 import java.io.IOException;
 
+import static org.junit.Assert.assertArrayEquals;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertTrue;
 
@@ -93,4 +97,37 @@ public class DiskFileUploadTest {
         assertEquals(2, f.getFile().length());
         f.delete();
     }
+
+    @Test
+    public void testAddContents() throws Exception {
+        DiskFileUpload f1 = new DiskFileUpload("file1", "file1", "application/json", null, null, 0);
+        try {
+            String json = "{\"foo\":\"bar\"}";
+            byte[] bytes = json.getBytes(CharsetUtil.UTF_8);
+            f1.addContent(Unpooled.wrappedBuffer(bytes), true);
+            assertEquals(json, f1.getString());
+            assertArrayEquals(bytes, f1.get());
+            File file = f1.getFile();
+            assertEquals((long) bytes.length, file.length());
+            FileInputStream fis = new FileInputStream(file);
+            try {
+                byte[] buf = new byte[bytes.length];
+                int offset = 0;
+                int read = 0;
+                int len = buf.length;
+                while ((read = fis.read(buf, offset, len)) > 0) {
+                    len -= read;
+                    offset += read;
+                    if (len <= 0 || offset >= buf.length) {
+                        break;
+                    }
+                }
+                assertArrayEquals(bytes, buf);
+            } finally {
+                fis.close();
+            }
+        } finally {
+            f1.delete();
+        }
+    }
 }