connection: Save cookiejar only when there's a Set-Cookie header in the response

osc/connection.py

@@ -484,6 +484,7 @@ class CookieJarAuthHandler(AuthHandlerBase):
         return False
 
     def process_response(self, url, request_headers, response):
+        if response.headers.get_all("set-cookie", None):
             self._cookiejar.extract_cookies(response, MockRequest(url, response.headers))
             self._cookiejar.save()
         self._unlock()