LU-4691 lmv: honor MDT index when creating volatile file

LU-4691 lmv: honor MDT index when creating volatile file

LMV should honor MDT index embedded in the name of volatile
file, then during hsm restore, the file under striped dir can
be restored to the right MDT.

Add test 405 in sanity-hsm to verify it.

Change-Id: I05170beee5255cf6581a2ea43edb6cc434a7cf8e
Signed-off-by: Wang Di <di.wang@intel.com>
Reviewed-on: http://review.whamcloud.com/10866
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: Henri Doreau <henri.doreau@cea.fr>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>