Fixed failure of os.rename after receiving file finished due to file not being closed.

Following error happen while at the end of _do_download called try_rename
WindowsError: [Error 32] The process cannot access the file because it is being used by another process

youtube-dl

@@ -640,6 +640,7 @@ class FileDownloader(object):
 			# Apply rate limit
 			self.slow_down(start, byte_counter)
 
+		stream.close()
 		self.report_finish()
 		if data_len is not None and str(byte_counter) != data_len:
 			raise ContentTooShortError(byte_counter, long(data_len))