LU-4991 test: check files in sanity 56s

In sanity 56s, run lfs getstripe -R to check
files in case of failure.

Change-Id: I52a55aae4e669c4b6af0bea869d75cc2cfff85c3
Signed-off-by: Wei Liu <wei3.liu@intel.com>
Reviewed-on: http://review.whamcloud.com/10360
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: Jian Yu <jian.yu@intel.com>