add code to possibly pull MPI_TAG_UB attribute value

I tested it this does not work with MPICH 3.1.1 (random values are
returned).

Signed-off-by: Sébastien Boisvert <boisvert@anl.gov>
remove whitespate

Signed-off-by: Sébastien Boisvert <boisvert@anl.gov>