LU-3326 tests: sync after file deleted in run_*.sh

LU-3326 tests: sync after file deleted in run_*.sh

In run_*.sh, call sync to flush any dirty pages to OST
if MDT has not sent the object destroy request to it,
which will shrink the available disk space gotten before
running the tests and cause -EIO error.

Signed-off-by: Hongchao Zhang <hongchao.zhang@intel.com>
Change-Id: Ia246122a5c3471b7cbea9cdaa7fad2ea4db856c5
Test-Parameters: alwaysuploadlogs \
envdefinitions=SLOW=yes,ENABLE_QUOTA=yes,REQFAIL=100,DURATION=28800 \
clientdistro=el6 ossdistro=el6 mdsdistro=el6 clientarch=x86_64 \
ossarch=x86_64 mdsarch=x86_64 clientcount=4 osscount=2 mdscount=2 \
mdssizegb=10 ostsizegb=10 austeroptions=-R failover=true iscsi=1 \
testlist=recovery-mds-scale
Reviewed-on: http://review.whamcloud.com/8071
Tested-by: Jenkins
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: Alex Zhuravlev <alexey.zhuravlev@intel.com>
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>