kernel - Fix pageout algorithm regression

* The pageout algorithm was trying to calculate when it might have
  to do 'a little extra' moving of pages active->inactive and wound
  up forcing an active->inactive queue run in all cases, even when
  the inactive queue was well over target.

* Remove the broken case.

* Greatly improves (as in restores) performance on systems with heavy
  paging and file caching activity.