Apply any comm layer maximum thread count.
Apply any comm layer maximum thread count.

If the comm layer imposes a maximum thread count, we should apply that
when we've got a symbolic CHPL_RT_NUM_THREADS_PER_LOCALE.

chizarlicious/chapel,hildeth/chapel,CoryMcCartan/chapel,CoryMcCartan/chapel,CoryMcCartan/chapel,hildeth/chapel,chizarlicious/chapel,chizarlicious/chapel,CoryMcCartan/chapel,CoryMcCartan/chapel,hildeth/chapel,chizarlicious/chapel,CoryMcCartan/chapel,chizarlicious/chapel,chizarlicious/chapel,hildeth/chapel,hildeth/chapel,hildeth/chapel,chizarlicious/chapel,hildeth/chapel,CoryMcCartan/chapel