The cleanup action for the FuVliUsbhubPdDevice is correct, but was not
conditionalized in the composite cleanup, which meant we would reboot twice
for a normal USB hub update.
Move the parent reboot into the right place, although this does mean we might
reboot twice in the rare event of scheduing a FuVliUsbhubPdDevice *and*
FuVliUsbhubDevice update in the same transaction -- but resetting the device
state between updates is arguably correct anyway...
