added MPI comment
added MPI comment

manjugv/ucx,sergsagal1/ucx_rocm,miked-mellanox/ucx,sergsagal1/ucx_rocm,miked-mellanox/ucx,shssf/ucx,manjugv/ucx,biddisco/ucx,abouteiller/ucx,abouteiller/ucx,shssf/ucx,miked-mellanox/ucx,biddisco/ucx,sergsagal1/ucx_rocm,shssf/ucx,manjugv/ucx,biddisco/ucx,abouteiller/ucx,abouteiller/ucx