LU-4970 tests: wait async LFSCK updates to be done

LU-4970 tests: wait async LFSCK updates to be done

There may be some async LFSCK updates in processing when the
test scripts check the reparation result. So make the scripts
to wait/retry until the async updates has been done or timeout.

Signed-off-by: Fan Yong <fan.yong@intel.com>
Change-Id: I71a1986de432631ec7158a7e90797c46ae672812
Reviewed-on: http://review.whamcloud.com/11590
Tested-by: Jenkins
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Lai Siyao <lai.siyao@intel.com>
Reviewed-by: Alex Zhuravlev <alexey.zhuravlev@intel.com>