request: paused upload on completed download, assess connection

A transfer with a completed download that is still uploading needs to
check the connection state when it is PAUSEd, since connection
close/errors would otherwise go unnoticed.

Reported-by: Sergey Bronnikov
Fixes #13260
Closes #13271

lib/request.c

@@ -395,6 +395,7 @@ CURLcode Curl_req_send_more(struct Curl_easy *data)
   result = req_flush(data);
   if(result == CURLE_AGAIN)
     result = CURLE_OK;
+
   return result;
 }