LU-8200 test: improve sanityn.sh 33c

LU-8200 test: improve sanityn.sh 33c

If transaction is committed before unlock, lock won't be saved. So
trigger Sync-Lock-Cancel twice in sanityn.sh 33c, it's unlikely to
fail both.

This patch is back-ported from the following one:
Lustre-commit: 04c4b9c2a121e76881f8b387a4721069418c92f0
Lustre-change: https://review.whamcloud.com/31673

Test-Parameters: trivial clientcount=2 mdscount=2 mdtcount=4 \
osscount=1 ostcount=8 mdtfilesystemtype=zfs ostfilesystemtype=zfs \
testlist=sanityn

Signed-off-by: Lai Siyao <lai.siyao@intel.com>
Change-Id: I5c99e5a8261df8c9f463aea7ed67df95baaf3e6c
Reviewed-on: https://review.whamcloud.com/33057
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Lai Siyao <lai.siyao@whamcloud.com>
Reviewed-by: James Nunez <jnunez@whamcloud.com>
Reviewed-by: John L. Hammond <jhammond@whamcloud.com>