LU-746 obdfilter-survey FAIL: test_1b ost4: hndls expected > 8, have 2

LU-746 obdfilter-survey FAIL: test_1b ost4: hndls expected > 8, have 2

obdfilter-survey.sh checks jbd proc stats after survey, but it
doesn't take obd cleanup time into account, so the stats
collected may not reflect the data of survey test. Save run time
of survey test, and collect stats of (run_time/4) ago to fix this.

Change-Id: Ib0b55693d13da172ca476ca79013a8a2e9dd81ca
Signed-off-by: Lai Siyao <laisiyao@whamcloud.com>
Reviewed-on: http://review.whamcloud.com/1534
Tested-by: Hudson
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Johann Lombardi <johann@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>
Reviewed-by: Liang Zhen <liang@whamcloud.com>