Fixed error rechecking & forced re-cache on update

- Fixed re-checking the state of a manga after an error, where
previously it would not always try to re-check if it could now be
fetched properly.
- Changed the force re-cache that is used to avoid problems when
something big changes to only force the re-cache if the update is a
major update such as from x.3.x.x to x.4.x.x