If --continue is not enabled, set resume_len to zero.

This corrects the reporting of download progress (which previously
started at a value greater than zero).

youtube-dl

@@ -877,7 +877,6 @@ class FileDownloader(object):
 
 		tmpfilename = self.temp_name(filename)
 		stream = None
-		open_mode = 'wb'
 
 		# Do not include the Accept-Encoding header
 		headers = {'Youtubedl-no-compression': 'True'}
@@ -890,11 +889,14 @@ class FileDownloader(object):
 		else:
 			resume_len = 0
 
-		# Request parameters in case of being able to resume
-		if self.params.get('continuedl', False) and resume_len != 0:
+		open_mode = 'wb'
+		if resume_len != 0:
+			if self.params.get('continuedl', False):
 				self.report_resuming_byte(resume_len)
 				request.add_header('Range','bytes=%d-' % resume_len)
 				open_mode = 'ab'
+			else:
+				resume_len = 0
 
 		count = 0
 		retries = self.params.get('retries', 0)