We're currently incrementing /proc/vmstat:pgalloc in front of the
per-cpu page queues, and incrementing /proc/vmstat:pgfree behind the
per-cpu queues.  So they get out of whack.

Change it so that we increment the counters each time someone requests
a page.  ie: they're both in front of the queues.

Also, remove a duplicated prep_new_page() call and as a consequence,
drop the whole additional list walk in rmqueue_bulk().