Fix target device_id when other device is detected

When the enforced/stored device_id is already used, use another one free.

src/minisatip.c

@@ -2031,7 +2031,7 @@ int readBootID() {
  uuid4_generate(opts.uuid);
  }
 
- if (opts.device_id < 1) {
+ if (opts.device_id < local_device_id) {
  opts.device_id = local_device_id;
  }