Merge pull request #1800 from klemensn/rtsp-listener-exit-segfault

Fix crash on double pthread_cancel(3) on exit (detected on OpenBSD).

rtsp.c

@@ -5694,7 +5694,7 @@ void *rtsp_listen_loop(__attribute((unused)) void *arg) {
  } while (1);
  pthread_cleanup_pop(1); // should never happen
  } else {
- warn("could not establish a service on port %d -- program terminating. Is another instance of "
+ die("could not establish a service on port %d -- program terminating. Is another instance of "
  "Shairport Sync running on this device?",
  config.port);
  }