kernel - Require pages to be PQ_ACTIVE for quick vm_page soft refs

kernel - Require pages to be PQ_ACTIVE for quick vm_page soft refs

* Require the a VM page be ACTIVE when allowing a quick soft ref
  on it for a vm_fault().  If the page is not ACTIVE, the fault will
  access it normally and activate it.

  Previously the page could be ACTIVE or INACTIVE.

* This ensures that pages often-referenced by vm_fault do not accidently
  flow through states and get freed prematurely, causing light paging
  to unnecessarily stall active processes.