LU-9250 tests: add parallel-scale xdd test

LU-9250 tests: add parallel-scale xdd test

Patch adds parallel-scale xdd test.

Our customers report the Lustre issues hit during
xdd test. We need a flexible way to reproduce the
failures.

Author: Chennaiah Palla <chennaiah.palla@seagate.com>

Signed-off-by: Chennaiah Palla <chennaiah.palla@seagate.com>
Signed-off-by: Elena Gryaznova <c17455@cray.com>
Cray-bug-id: LUS-5206
Seagate-bug-id: MRP-3915
Test-Parameters: testlist=parallel-scale
Reviewed-by: Vladimir Saveliev <c17830@cray.com>
Reviewed-by: Elena Gryaznova <c17455@cray.com>
Change-Id: Ia4823aa8ce64aad3d43b2611b24f48a532b8796c
Reviewed-on: https://review.whamcloud.com/26176
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Alexander Zarochentsev <c17826@cray.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>