LU-9073 gss: quiet insecure key file warning

LU-9073 gss: quiet insecure key file warning

Quiet spurious warning about insecure file access mode, because the
st_mode contains file type as well.

Signed-off-by: Andreas Dilger <andreas.dilger@intel.com>
Change-Id: If347eb3de67074269de4fe279ba4a849e03ebbe5
Reviewed-on: https://review.whamcloud.com/25201
Tested-by: Jenkins
Reviewed-by: Nathan Lavender <nblavend@iu.edu>
Reviewed-by: James Simmons <uja.ornl@yahoo.com>
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>