LU-15709 tests: t-f stopall() defect: num not initialized

LU-15709 tests: t-f stopall() defect: num not initialized

The following test demonstrates the defect (OSTCOUNT=2):
  test_0A () {
        local num=100
        echo $num
        stopall
        echo $num after stopall
  }
Result:
  == sanity test 0A: num ===
  100
  Stopping clients: fre0107,fre0108 /mnt/lustre (opts:)
  ...
  2 after stopall

Fixes: d2d56f38da (" - make HEAD from b_post_cmd3")
Test-Parameters: trivial
Signed-off-by: Elena Gryaznova <elena.gryaznova@hpe.com>
HPE-bug-id: LUS-10864
Reviewed-by: Alexander Zarochentsev <alexander.zarochentsev@hpe.com>
Reviewed-by: Artem Blagodarenko <artem.blagodarenko@hpe.com>
Change-Id: I46648c741943f219c03f3501585051e285365578
Reviewed-on: https://review.whamcloud.com/46957
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>