cleanup: fix stale cask detection.
cleanup: fix stale cask detection.

This method is also run to check formulae and if a formula and cask have
the same name (e.g. `cmake`) then this method would mark all formulae
downloads to being stale.

Instead, check the `dirname` (which we're using for globs anyway) to
double check that this is definitely a stale cask.

claui/brew,konqui/brew,Homebrew/brew,reitermarkus/brew,MikeMcQuaid/brew,reitermarkus/brew,nandub/brew,vitorgalvao/brew,EricFromCanada/brew,sjackman/homebrew,mahori/brew,Homebrew/brew,Homebrew/brew,Homebrew/brew,JCount/brew,reitermarkus/brew,konqui/brew,MikeMcQuaid/brew,mahori/brew,JCount/brew,nandub/brew,claui/brew,vitorgalvao/brew,sjackman/homebrew,konqui/brew,mahori/brew,vitorgalvao/brew,EricFromCanada/brew,JCount/brew,JCount/brew,EricFromCanada/brew,claui/brew,vitorgalvao/brew,nandub/brew,MikeMcQuaid/brew,sjackman/homebrew,MikeMcQuaid/brew,nandub/brew,konqui/brew,EricFromCanada/brew,mahori/brew,claui/brew,reitermarkus/brew,sjackman/homebrew