Fix a pair of bugs introduced in r356002. When we reclaim physical pages we
allocate them with VM_ALLOC_NOOBJ which means they are not busy. For now
move the busy assert for the new page in vm_page_replace into the public
api and out of the private api used by contig reclaim. Fix another issue
where we would leak busy if the page could not be removed from pmap.

Reported by: pho
Discussed with: markj