Increase crawler timeout from 2h to 3h.
    
    Since MM2 is in production about 140 mirrors have been auto-disabled
    due to crawler timing out after 2 hours (default). Try if it works
    better with 3 hours. This in combination with the previous commit
    to decrease the load on the database should help to auto disable
    less good mirrors. Especially mirrors who mirroring almost
    everything can hardly be crawled within the 2 hour limit. Unfortunately
    the limit is per host and not category.