[Bug] Prime Hub display turns back on after shutdown()

[laurensvalk]

Describe the bug

When using hub.system.shutdown(), you can see the square stop sign flash back on briefly. If USB is connected, it stays on permanently. The hub is in "off-mode", though, as seen from the hub status light.

When using the button, it does turn off correctly, and stays off. Shutdown after 3 minute timeout also works correctly.

To reproduce

Reproduce with single-boot for simplicity.

Run this:

from pybricks.hubs import ThisHub
from pybricks.tools import wait

hub = ThisHub()

print(hub.system.reset_reason())

wait(100)

hub.system.shutdown()

Expected behavior
Expected display to turn off and stay off, just as when holding the button.