### Description

I use TCP sockets to relay calls to backend servers. Also, I have enabled `tcp_reuse_port` and enabled `socket` attribute in dispatcher settings. INVITE messages to backend servers are now properly send from port 5060.

### Expected behavior For all messages are used the same TCP socket and same source port for all messages (including OPTIONS).

#### Actual observed behavior But initial OPTIONS (before the first call send) uses a random source port.

### Additional Information

* **Kamailio Version** - output of `kamailio -v`

used current c503d2bd31a580138a67f1d4a265ccde5791d271 with small customization.

* **Operating System**: aarch64 ``` [root@sbc-a0 ~]# cat /etc/os-release NAME="CentOS Linux" VERSION="8" ID="centos" ID_LIKE="rhel fedora" VERSION_ID="8" PLATFORM_ID="platform:el8" PRETTY_NAME="CentOS Linux 8" ANSI_COLOR="0;31" CPE_NAME="cpe:/o:centos:centos:8" HOME_URL="https://centos.org/" BUG_REPORT_URL="https://bugs.centos.org/" CENTOS_MANTISBT_PROJECT="CentOS-8" CENTOS_MANTISBT_PROJECT_VERSION="8" ```