LU-7763 tests: improve sanityn 33d

Sanityn.sh 33d verifies that CoS (Commit-on-Sharing) for DNE, but if
transaction commits before unlock, CoS will not be triggered. To
avoid this, do all tests twice, it's unlikely that both will fail.

This patch is back-ported from the following one:
Lustre-commit: 9d49453b
Lustre-change: https://review.whamcloud.com/31946



Test-Parameters: trivial testlist=sanityn mdscount=2 mdtcount=4

Change-Id: If20670321e4bda9763b3794145d62a7264e7cef6
Signed-off-by: Lai Siyao <lai.siyao@intel.com>
Reviewed-on: https://review.whamcloud.com/32937


Tested-by: Jenkins
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Lai Siyao <lai.siyao@whamcloud.com>
Reviewed-by: John L. Hammond <jhammond@whamcloud.com>