tm: flag core to use forced socket when uac socket is set

- without flag SND_F_FORCE_SOCKET probing by dispatcher module
  and route script function t_uac_send() will choose incorrect source socket

(cherry picked from commit 7da5e5b)
(cherry picked from commit fc77e25)
(cherry picked from commit c5becaa)

modules/tm/uac.c

@@ -250,6 +250,12 @@ static inline int t_uac_prepare(uac_req_t *uac_r,
 	/* new message => take the dialog send_socket if set, or the default
 	  send_socket if not*/
 	SND_FLAGS_INIT(&snd_flags);
+
+	if (uac_r->dialog->send_sock != NULL)
+	{
+		snd_flags.f |= SND_F_FORCE_SOCKET;
+	}
+
 #ifdef USE_DNS_FAILOVER
 	if (cfg_get(core, core_cfg, use_dns_failover)){
 		dns_srv_handle_init(&dns_h);