nfqueue: inject fake packet on timeout

Fixes nfqueue and delayed-detect.

On systems with small amount of traffic (or with no traffic at all)
nfqueue with 'delayed-detect' enabled hanged in 'workers' mode.

Bug #2362.

src/source-nfq.c

@@ -916,6 +916,9 @@ static void NFQRecvPkt(NFQQueueVars *t, NFQThreadVars *tv)
             /* no error on timeout */
             if (flag)
                 NFQVerdictCacheFlush(t);
+
+            /* inject a fake packet on timeout */
+            TmThreadsCaptureInjectPacket(tv->tv, tv->slot, NULL);
         } else {
 #ifdef COUNTERS
             NFQMutexLock(t);