[IPTorrents] Fixed error when searching for episodes

Fixed an error when you try to search episodes with iptorrents as provider. 
It seems like `seeders` wasn't updated to `torrent_seeders`.
Error obtained before:
```
2013-09-24 15:22:59 SEARCHQUEUE-BACKLOG-84676 :: Failed parsing IPTorrents Traceback: Traceback (most recent call last):
  File "/samba/apps/Sick-Beard/sickbeard/providers/iptorrents.py", line 195, in _doSearch
    if mode != 'RSS' and seeders == 0:
NameError: global name 'seeders' is not defined

```
Tried and it's working.