LU-3853 tests: mpiexec requires strict global/local args order

LU-3853 tests: mpiexec requires strict global/local args order

Put -machinefile option ahead of other mpiexec options, since some
version of mpiexec (at least 1.90) requests global options be put
before its local options, and -machinefile is a global options.

Signed-off-by: Bobi Jam <bobijam.xu@intel.com>
Change-Id: Ib188881a78a2b345552e8c6070f7dfa7a086ce5d
Reviewed-on: http://review.whamcloud.com/7493
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Jian Yu <jian.yu@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>