LU-9271 tests: remove unnecessary sanity-scrub test delay

In sanity-scrub test_5, we want to check the OI scrub state machine.
For that, we inject some failure stub to delay the test for checking
status. But sometimes, we want to check the status within some short
time that may be not enough because of the injected test delay. This
patch removes one unnecessary status checking since it has been done
in former check. On the other hand, the subsequent checking also can
indicate the correctness of the skipped status.

Test-parameters: trivial

Signed-off-by: Fan Yong <fan.yong@intel.com>
Change-Id: I14b5096db3d7ca255f3de1a8853dde85ead54215
Reviewed-on: https://review.whamcloud.com/26457
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Jian Yu <jian.yu@intel.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>