Fix scheduled sorting/filtering bug on started and stopped views in rtorrent

[chros73]

started and stopped views are special in rtorrent.
If view.filter or view.sort method is scheduled on one of them then it triggers massive scheduler bug that leads to various tracker communication problems (at least).
Actually the main cause of this is view.filter.

Solution: ignore view.filter method with started and stopped views. (These views aren't filtered by default anyway and if one tries to do it then it triggers this bug.)

(Refers to: rakshasa#449 )