add delay for volte test

tests/volte/abts-main.c

@@ -56,6 +56,8 @@ static void test_fd_logger_handler(enum fd_hook_type type, struct msg * msg,
 
 void test_terminate(void)
 {
+    ogs_msleep(50);
+
     pcscf_fd_final();
     testpacket_final();
     ogs_sctp_final();