WikiaDataAccess cache time bugfix

WikiaDataAccess::cache had small bug, so data was cached for longer time that it was supposed to be (2 times longer)

WikiaDataAccess::cacheWithLock was cached for even longer time but it's wasn't affected by this bug because of complex logic checking when cache is invalid

This pull request fixes problem mentioned above.

@Wyvek @hakubo @wladekb please take a look and correct me if something is wrong.