Two changes to vm_map_delete:

Two changes to vm_map_delete:

1. Don't bother checking object->ref_count == 1 in order to set
OBJ_ONEMAPPING.  It's a waste of time.  If object->ref_count == 1,
vm_map_entry_delete will "run-down" the object and its pages.

2. If object->ref_count == 1, ignore OBJ_ONEMAPPING.  Wait for
vm_map_entry_delete to "run-down" the object and its pages.
Otherwise, we're calling two different procedures to delete
the object's pages.

Note: "vmstat -s" will once again show a non-zero value
for "pages freed by exiting processes".