LU-10357 hsm: open file to be archived before starting

LU-10357 hsm: open file to be archived before starting

In the archive case of llapi_hsm_action_begin(), open the file to be
archived before calling the LL_IOC_HSM_COPY_START ioctl. Store the
open FD in struct hsm_copyaction_private, return a dup of it
llapi_hsm_action_get_fd(), and close it in
llapi_hsm_action_end(). Calling open() first avoids 3 extra RPCs
(MDS_GETATTR, LDLM_ENQUEUE for layout to get data version,
LDLM_ENQUEUE for fstat()) when archiving.

Signed-off-by: John L. Hammond <john.hammond@intel.com>
Change-Id: Idea0a7f4cb63bd9d712ff2ce9fcb59a3b278d0f2
Reviewed-on: https://review.whamcloud.com/30456
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Quentin Bouget <quentin.bouget@cea.fr>
Reviewed-by: Dmitry Eremin <dmitry.eremin@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>