LU-3634 llapi: Fix returned value of llapi_hsm_copy_start/end.

Both function were doing a ioctl and were returning ioctl()
return code instead of returning errno.

Signed-off-by: Aurelien Degremont <aurelien.degremont@cea.fr>
Change-Id: Ibd4c6f5188bb50e7fa8875e2d4fa3442c2c69888
Reviewed-on: http://review.whamcloud.com/7109
Tested-by: Hudson
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Faccini Bruno <bruno.faccini@intel.com>
Reviewed-by: John L. Hammond <john.hammond@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>