#licensing

Device limit counts first and saves later, and the test never sends two at once

The licensing code I shipped checks how many devices a key already has, then inserts the new one in a separate step, so two activations racing for the last slot can both get in. The test activates devices one at a time and can't see it, a device racing itself gets a server error, and a key-only check passes for keys never bound anywhere. I found this by reading, not by running anything concurrent.