usb1: Detach finalizer on duplicate registration in *.__registerFinalizer
usb1: Detach finalizer on duplicate registration in *.__registerFinalizer

Also, make the detection mendatory. It should only trigger on an internal
bug, so an assertion was kind of appropriate... But not detecting this
(when running on a python with assertions disabled) could lead to
double-frees.

vpelletier/python-libusb1,vpelletier/python-libusb1