Fix make_dir so it chmods only if new dir created
Fix make_dir so it chmods only if new dir created

Before, it led to permission denied exceptions when /dev/shm/bifrost had
been created by someone else. (We create it 0777 so can just proceed to
use it even if owner is different.)

ledatelescope/bifrost,ledatelescope/bifrost,ledatelescope/bifrost,ledatelescope/bifrost