LU-9403 mdt: prevent HSM leak on re-archive

LU-9403 mdt: prevent HSM leak on re-archive

In mdt_hsm_is_action_compat() if the file to be archived already
exists in some backend archive then ensure that the re-archive
uses the same backend archive.

Signed-off-by: John L. Hammond <john.hammond@intel.com>
Change-Id: Ifc0ef03264a20557c31df7add9e34a1dc1f0c814
Reviewed-on: https://review.whamcloud.com/26866
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Henri Doreau <henri.doreau@cea.fr>
Reviewed-by: Faccini Bruno <bruno.faccini@intel.com>
Reviewed-by: Quentin Bouget <quentin.bouget@cea.fr>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>