LU-4981 test: Fix IO redirect in sanity 133g

Redirect error message of badarea_io to /dev/null in
133g.

Signed-off-by: wang di <di.wang@intel.com>
Change-Id: If75628a6502511684886ffc2f1eb9711b59991de
Reviewed-on: http://review.whamcloud.com/10181
Tested-by: Jenkins
Reviewed-by: John L. Hammond <john.hammond@intel.com>
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Jian Yu <jian.yu@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>