[sr-dev] [kamailio/kamailio] authentificated INVITE badly managed when topos is activated (#2629)

### Description

If topos is activated and kamailio responds a 407 "proxy authentication required" to a initial INVITE, INVITE received after with credentials (MD5 response in Proxy-Authorization header) is badly managed. Credentials are never validated and kamailio responds 407 again. If topoh is used instead topos all works fine and credential are validated.

### Troubleshooting

#### Reproduction Always.

#### SIP Traffic

### Possible Solutions I have tested with official kamailio 5.4.3-0.

* **Operating System**: centos 7 (3.10.0-693.11.1.el7.x86_64)