Code review comment for lp:~ltrager/maas/stress_ng_tests

I haven't reviewed the rest of this branch, but I'd like to suggest a policy: all shell scripts should be run with bash. Bash is fairly unpleasant for anything non-trivial, but /bin/sh in all its forms is hostile to sanity and happiness. Shell scripts are a blight, but if we must write them then let's at least stick to the least insane of the ubiquitous ones.