LU-10041 tests: sanity/51 to cleanup properly

LU-10041 tests: sanity/51 to cleanup properly

sanity/51 should cleanup properly in case of failure

Test-Parameters: trivial testlist=sanity ostfilesystemtype=zfs mdtfilesystemtype=zfs
Test-Parameters: trivial testlist=sanity mdscount=2 mdtcount=4

Lustre-change: https://review.whamcloud.com/29246
Lustre-commit: 0d5ceb891e904cc9bab3a6b5ce0944b8bab06975

Change-Id: Ib1c0e1a116a6802f2bf25d665be5c076ae07c8b8
Signed-off-by: Alex Zhuravlev <alexey.zhuravlev@intel.com>
Reviewed-by: James Nunez <james.a.nunez@intel.com>
Reviewed-by: Wei Liu <wei3.liu@intel.com>
Signed-off-by: Minh Diep <minh.diep@intel.com>
Reviewed-on: https://review.whamcloud.com/30023
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: John L. Hammond <john.hammond@intel.com>