LU-879 mds: Add a few rename stats under /proc

LU-879 mds: Add a few rename stats under /proc

1. Add samedir_rename in /proc/fs/lustre/mds/lustre-MDT0000/stats
to collect stats of same dir rename.
2. Add crossdir_rename in /proc/fs/lustre/mds/lustre-MDT0000/stats
to collect stats of cross dir rename.
3. Add /proc/fs/lustre/mds/lustre-MDT0000/rename_stats(YAML format)
to collect stats of rename stats happened on different size
directories.
The size of directories under which files are being removed.
With these patches, it will find out how many renames take place
in the same directory compared to how many renames are between
So during DNE implementation, we can know how rename may be
affected by DNE remote directories and large striped directories.

Signed-off-by: Wang Di <di.wang@whamcloud.com>
Change-Id: I4452ce196802c5724607455e0a9b4b372b06f159
Reviewed-on: http://review.whamcloud.com/1878
Tested-by: Hudson
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>