MPICH doesn't parse deduplicated hostfiles

[lukemartinlogan]

MPI doesn't standardize the hostfile format. I built the hostfile in a way I thought was portable across MPI versions. I was wrong.

MPICH 4.0.2 does not parse deduplicated hostfile lists properly. E.g., ares-comp-[22-30] would require expanding to ares-comp-22, ares-comp-23, ... We should either make a tmpfile with the expanded host list or use the CLI.