LU-6385 tests: Sync OSTs between tests in obdfilter-survey

osd-ldiskfs and osd-zfs operate differently with regards to writeback
cache.  This adds a force sync between test runs so that a test list
of "write read" will have all writes finished before reads starts for
both ldiskfs and zfs.

Signed-off-by: Nathaniel Clark <nathaniel.l.clark@intel.com>
Change-Id: I3414a595220d9eb65145f8246ed5e243c112b866
Reviewed-on: http://review.whamcloud.com/14143


Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Alex Zhuravlev <alexey.zhuravlev@intel.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>

lustre-iokit/obdfilter-survey/obdfilter-survey

@@ -525,6 +525,12 @@ for ((rsz = $rszlo; rsz <= $rszhi; rsz*=2)); do
 
 			# run tests
 			for test in ${tests[@]}; do
+				# Sync all outstanding data
+				for host in ${ost_hosts[@]}; do
+					remote_shell $host \
+					    "lctl set_param -n osd*.*OST*.force_sync 1"
+				done
+
 				declare -a pidarray
 				for host in ${unique_hosts[@]}; do
 					echo "starting run for test: $test rsz: $rsz " \