LU-3534 update: change sync updates to async updates

LU-3534 update: change sync updates to async updates

1. change sync updates to async updates.

2. add tests(110,111,112,115) in replay-single to test
async update recovery.

3. Add replay-barrier for those old DNE replay tests,
so all of MDTs can be recoveried correctly.

4. enable DNE failover to dbench test (replay-single.sh 70b).

Change-Id: Ibe1ca42d60c7a0ec870b9cf4a70a71adc663b951
Signed-off-by: Wang Di <di.wang@intel.com>
Reviewed-on: http://review.whamcloud.com/12450
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: James Simmons <uja.ornl@yahoo.com>
Reviewed-by: Alex Zhuravlev <alexey.zhuravlev@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>