kernel - Do not use shared tokens for kernel_map

kernel - Do not use shared tokens for kernel_map

* This primarily handles a case where i386 systems can deadlock on a
  shared token -> exclusive token sequence during a page fault, because
  the i386 pmap code uses kernel_object to manage page table pages.

  x86-64 page fault code does not but for now just make the change globally.

* Should not effect performance

* Change the default for vm_

* Change the default for vm.shared_fault back to 1.

Reported-by: ejc
Submitted-by: vsrinivas