LU-7169 tests: check disk corruption during failover

LU-7169 tests: check disk corruption during failover

It is a debug patch for conf-sanity test_84. It is suspected
that there is some disk corruption during the MDT0 failover.

Test-Parameters: mdsfilesystemtype=ldiskfs mdtfilesystemtype=ldiskfs ostfilesystemtype=ldiskfs testlist=conf-sanity,conf-sanity,conf-sanity
Signed-off-by: Fan Yong <fan.yong@intel.com>
Change-Id: I7e20f26e1ecee483474ace44c8284b5776f3c602
Reviewed-on: http://review.whamcloud.com/16664
Tested-by: Jenkins
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: Jian Yu <jian.yu@intel.com>
Tested-by: Maloo <hpdd-maloo@intel.com>