LU-2033 scrub: lookup server local files by name

LU-2033 scrub: lookup server local files by name

after backup/restore ldiskfs's OI becomes invalid (inodes
change). OI scrubber scans a filesystem to rebuild OI. this
can take quite long. to be able to start MDS earlier (right
after restore) MDS should lookup by name all internal files
required for startup as name->inode mapping is preserved by
backup/restore. this patch make local object library to
lookup a file storing last used fid within a given sequence.

the patch also fixes sanity-scrub/11 to expect skipping of
files created + directory + per-ost llog objects.

Signed-off-by: Fan Yong <yong.fan@whamcloud.com>
Change-Id: I56179c03279062464960af73de031f13d31bac14
Reviewed-on: http://review.whamcloud.com/4106
Tested-by: Hudson
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>