IgorrG created an issue (kamailio/kamailio#4266)
### Description
While implementing mid-register inspired by pull request (https://github.com/kamailio/kamailio/pull/3360) we found the case when it goes impossible to handle responses for registrar servers. In case some of registrars busy and respond with 401 after 200ok received - it is not possible using any routes and configuration options to handle responses received in branch transactions.
According to documentation I think that setting wt_timer should allow to absorb and handle responses on failure-route while transaction kept in memory. In fact wt_timer does not affect handling responses in any way.
### Troubleshooting
To reproduce this case we have configured sipp to response instant with 200ok on registration request.
#### Reproduction
To reproduce issue SIPP could be setup as one of the dispatcher nodes with instant 200ok reply to register. Kamailio should use following configuration snippet: https://github.com/ovoshlook/kamailio-mid-registrar-config-snippets/blob/mas...
#### Log Messages
REGISTER|401tm [t_lookup.c:912]: t_reply_matching(): t_reply_matching: hash 12337 label 0 branch 1 REGISTER|401tm [t_lookup.c:986]: t_reply_matching(): reply (0x7f1fc67f83a8) matched an active transaction (T=0x7f1fc0f0f740)! REGISTER|401tm [t_lookup.c:1122]: t_check_msg(): msg (0x7f1fc67f83a8) id=13/1915035 global id=13/1915035 T end=0x7f1fc0f0f740 REGISTER|401tm [t_reply.c:2363]: reply_received(): transaction found - T:0x7f1fc0f0f740 branch:1 REGISTER|401tm [t_reply.c:2376]: reply_received(): original status uas=200, uac[1]=0 local=0 is_invite=0) REGISTER|401tm [t_reply.c:1363]: t_should_relay_response(): ->>>>>>>>> T_code=200, new_code=401 REGISTER|401tm [t_reply.c:1374]: t_should_relay_response(): final reply already sent REGISTER|401tm [t_reply.c:1625]: t_should_relay_response(): finished with rps discarded - uas status: 200
### Possible Solutions
<!-- If you found a solution or workaround for the issue, describe it. Ideally, provide a pull request with a fix. -->
### Additional Information
* **Kamailio Version**
``` version: kamailio 5.6.4 (x86_64/linux) flags: USE_TCP, USE_TLS, USE_SCTP, TLS_HOOKS, USE_RAW_SOCKS, DISABLE_NAGLE, USE_MCAST, DNS_IP_HACK, SHM_MMAP, PKG_MALLOC, Q_MALLOC, F_MALLOC, TLSF_MALLOC, DBG_SR_MEMORY, USE_FUTEX, FAST_LOCK-ADAPTIVE_WAIT, USE_DNS_CACHE, USE_DNS_FAILOVER, USE_NAPTR, USE_DST_BLOCKLIST, HAVE_RESOLV_RES, TLS_PTHREAD_MUTEX_SHARED ADAPTIVE_WAIT_LOOPS 1024, MAX_RECV_BUFFER_SIZE 262144, MAX_URI_SIZE 1024, BUF_SIZE 65535, DEFAULT PKG_SIZE 8MB poll method support: poll, epoll_lt, epoll_et, sigio_rt, select. id: unknown compiled on 16:35:08 Jun 5 2023 with gcc 10.2.1
```
* **Operating System**:
``` No LSB modules are available. Distributor ID: Debian Description: Debian GNU/Linux 11 (bullseye) Release: 11 Codename: bullseye
Linux pbxKamaTest 5.10.0-23-amd64 #1 SMP Debian 5.10.179-1 (2023-05-12) x86_64 GNU/Linux
```