LU-1371 ldiskfs: fix osd_it_iam_rec() to support binary keys

LU-1371 ldiskfs: fix osd_it_iam_rec() to support binary keys

osd_it_iam_rec() assumes a string key and does not support binary key.

Signed-off-by: Johann Lombardi <johann@whamcloud.com>
Change-Id: I1a09c9b9ad53e593cad642b6ae8a7d417ea83c9d
Reviewed-on: http://review.whamcloud.com/2647
Tested-by: Hudson
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Liang Zhen <liang@whamcloud.com>
Reviewed-by: wangdi <di.wang@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>