PERFTEST: Add option to force MPI/non-MPI run.
PERFTEST: Add option to force MPI/non-MPI run.

shssf/ucx,manjugv/ucx,sergsagal1/ucx_rocm,abouteiller/ucx,manjugv/ucx,sergsagal1/ucx_rocm,shssf/ucx,manjugv/ucx,abouteiller/ucx,abouteiller/ucx,shssf/ucx,sergsagal1/ucx_rocm,abouteiller/ucx