nfq: clear memory of queue before using it

Avoids using uninitialized memory. Show showed itself
in nonsense values in counters, and in nfq_handle_packet
errors that were likely the result of passing uninitialized
memory to the nfq API.

Bug 3263.
Bug 3120.

Fixes: b2a6c60dee ("source-nfq: increase maximum queues number to 65535")

src/source-nfq.c

@@ -847,6 +847,7 @@ int NFQRegisterQueue(const uint16_t number)
     ntv->nfq_index = receive_queue_num;
 
     nq = &g_nfq_q[receive_queue_num];
+    memset(nq, 0, sizeof(*nq));
     nq->queue_num = number;
     receive_queue_num++;
     SCMutexUnlock(&nfq_init_lock);