Fix concerns from Kosaki Motohiro (merge with compaction core)
o Fewer pages are isolated. Hence, cc->migrate_pfn in
isolate_migratepages() is updated slightly differently and the debug
checks change
o LRU lists are no longer rotated
o NR_ISOLATED_* is updated
o del_page_from_lru_list() is used instead list_move when isolated so
that the counters get updated correctly.
o Pages that fail to migrate are put back on the LRU promptly to avoid
being isolated for too long.
Signed-off-by: Mel Gorman<mel@xxxxxxxxx>