[v9_18] Handle ISC_R_SUCCESS on a deactivated response in udp_recv()
requested to merge 3300-dispatch-udp_recv-handle-deactivated-resp-returning-success-v9_18 into v9_18
There is a possibility for udp_recv() to be called with eresult
being ISC_R_SUCCESS, but nevertheless with already deactivated resp,
which can happen when the request has been canceled in the meantime.
Closes #3300 (closed)