LU-4713 test: Add a check to test_237 in sanity.sh

LU-4713 test: Add a check to test_237 in sanity.sh

This patch adds a check to test_237 in sanity.sh to check whether
write to the file succeeded or not.

Test-Parameters: clientdistro=sles11sp3 testlist=sanity envdefinitions=ONLY=237
Signed-off-by: Swapnil Pimpale <spimpale@ddn.com>
Change-Id: Id81f9bf01ead516c3b0e7f247ff71550d4a9847e
Reviewed-on: http://review.whamcloud.com/10088
Tested-by: Jenkins
Reviewed-by: Bob Glossman <bob.glossman@intel.com>
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>