LU-4980 tests: enhance sanity-scrub test_11

LU-4980 tests: enhance sanity-scrub test_11

If there are new objects created during the OI scrub re-scanning,
then the new created objects will not be skipped by OI scrub this
time. The test should record the total checked objects count for
each cycle scanning to avoid unnecessary check failure.

Signed-off-by: Fan Yong <fan.yong@intel.com>
Change-Id: I2bde83a5c03910216070cc23d01785624d829af4
Reviewed-on: http://review.whamcloud.com/10214
Tested-by: Jenkins
Reviewed-by: Bobi Jam <bobijam@gmail.com>
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Jian Yu <jian.yu@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>