g_tune_pme assumes an MPI environment is available
g_tune_pme -np 512 -nobench fails on machines (like BlueGene/Q) where you can only get an MPI environment via the queueing system. The routine that checks that mdrun works assumes it can do that check by running a quick MPI program, and does so regardless of -nobench.
Fixed g_tune_pme assumption that MPI is available
Refactored function with two distinct parts into two functions. This
makes it easy to call the part that checks that mdrun works only when
that check is necessary. Now g_tune_pme -np 512 -nobench works on
machines like BlueGene/Q where you might only be able to get the MPI
environment via the queuing system. g_tune_pme -nobench should work as