Fix imagevalidate error in create_image
boss:/usr/testbed/images> wap /usr/testbed/sbin/imagevalidate -d -u
emulab-ops/UBUNTU16-64-OSCN-O:0
Will process 1 images
Checking image 'emulab-ops/UBUNTU16-64-OSCN-O:0' ...
emulab-ops/UBUNTU16-64-OSCN-O:0: no image file found or cannot access
So then I did an imagerelease first (which copied the imagefile from ops
to boss), then redid the imagevalidate, and then imagevalidate worked.