nfq: suppress coverity thread warning

CID 1593187: (#1 of 1): Data race condition (MISSING_LOCK)
2. missing_lock: Accessing (*p).nfq_v.mark without holding lock Packet_.persistent.tunnel_lock. Elsewhere, NFQPacketVars_.mark is written to with Packet_.persistent.tunnel_lock held 2 out of 5 times (2 of these accesses strongly imply that it is necessary).

No concurrency happening on non-tunnel packet, so no locking needed.

src/source-nfq.c

@@ -1231,6 +1231,7 @@ TmEcode VerdictNFQ(ThreadVars *tv, Packet *p, void *data)
         /* coverity[missing_lock] */
         p->nfq_v.verdicted = true;
 
+        /* coverity[missing_lock] */
         int ret = NFQSetVerdict(p, p->nfq_v.mark, p->nfq_v.mark_modified);
         if (ret != TM_ECODE_OK) {
             return ret;