LU-4178 tests: add messages to sanity-hsm

LU-4178 tests: add messages to sanity-hsm

Add messages in case of file creation failure so we
can diagnose the failure.

Signed-off-by: JC Lafoucriere <jacques-charles.lafoucriere@cea.fr>
Change-Id: I080c4cbb6bfe5a65d964f32a36d7c1dba35d0c27
Reviewed-on: http://review.whamcloud.com/8113
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: James Simmons <uja.ornl@gmail.com>
Reviewed-by: James Nunez <james.a.nunez@intel.com>
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>