Decrease valgrind over-subscription
Decrease valgrind over-subscription

Drop from 10 down to 8 instances. We over-subscribed with valgrind testing
because valgrind is slow. Valgrind serializes things so it's pretty safe to run
over-subscribed because different processes won't be stepping on each other.

However, chap11 (where valgrind currently runs) only has 8 physical cores (16)
logical. I'm decreasing over-subscription to 8 instances so the hyperthreads
don't have to contend with physical threads. Hopefully this resolves the recent
do_smu timeout without increasing overall running time.

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