DownloadTask should manage fd properly

[dozono]

If the first download validation failed, the next retry will have problem with the closed fd.

[portwatcher]

An error related with it goes like this:

[ERROR] [2021/7/31上午1:37:20] Uncaught Exception
[ERROR] [2021/7/31上午1:37:20] RangeError [ERR_OUT_OF_RANGE]: The value of "fd" is out of range. It must be >= 0 && <= 2147483647. Received -1
[CONSOLE]     at Object.write (fs.js:641:3)
[CONSOLE]     at WriteStream._write (internal/fs/streams.js:396:13)
[CONSOLE]     at writeOrBuffer (internal/streams/writable.js:358:12)
[CONSOLE]     at WriteStream.Writable.write (internal/streams/writable.js:303:10)
[CONSOLE]     at IncomingMessage.ondata (internal/streams/readable.js:719:22)
[CONSOLE]     at IncomingMessage.emit (events.js:327:22)
[CONSOLE]     at IncomingMessage.Readable.read (internal/streams/readable.js:519:10)
[CONSOLE]     at flow (internal/streams/readable.js:992:34)
[CONSOLE]     at resume_ (internal/streams/readable.js:973:3)
[CONSOLE]     at processTicksAndRejections (internal/process/task_queues.js:80:21) {
[CONSOLE]   code: 'ERR_OUT_OF_RANGE'
[CONSOLE] }

[ci010]

Should be fixed in new version.