LU-11496 tests: start_client_loads () fix

LU-11496 tests: start_client_loads () fix

recovery-*-scale tests are not functional with LOADS=IOR
because of MPIRUN and MPIRUN_OPTIONS are not set.
Patch fixes this defect.

Test-Parameters: trivial
Signed-off-by: Elena Gryaznova <c17455@cray.com>
Cray-bug-id: LUS-6220
Reviewed-by: Andriy Skulysh <c17819@cray.com>
Reviewed-by: Alexander Boyko <c17825@cray.com>
Change-Id: I9b6d3810978260c0cec4a5482f093f788651aac0
Reviewed-on: https://review.whamcloud.com/33339
Tested-by: Jenkins
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Alexandr Boyko <c17825@cray.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>