The NAT-PMP client resends a map the gateway has not answered within
250 ms, and the mock gateway records every request, so a slow mock put a
resent map where the test expected the unmap and failed it. The test now
looks for the lifetime-0 request among whatever arrives after the drop.
On Windows the mock's answer to that resend meets an already-closed
socket, and the next receive reports the bounce as a connection reset,
which ended the mock's loop before the unmap. It now carries on past it.
Michel de Graaf
3c5a3dd648