LU-2061 hsm: send HSM resquest to CDT

LU-2061 hsm: send HSM resquest to CDT

This patch implements the user interface to ask for hsm requests

It implements:
- lfs hsm_archive
- lfs hsm_restore
- lfs hsm_cancel
- lfs hsm_remove
- lfs hsm_release

The matching llapi call:
- llapi_hsm_user_request_alloc()
- llapi_hsm_request()

related MDS functions:
- mdt_hsm_request()

and the MDS RPC:
- MDS_HSM_REQUEST

Signed-off-by: JC Lafoucriere <jacques-charles.lafoucriere@cea.fr>
Change-Id: I635f6e0518ec12c359dbb528c3a61216650d952d
Reviewed-on: http://review.whamcloud.com/5030
Reviewed-by: Johann Lombardi <johann.lombardi@intel.com>
Tested-by: Hudson
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>