examples/ubuntu: add --disable_privet flag - set dns_sd, wifi and http_server to nullptr Bug: 24408713 Change-Id: I2018043c2d575c777e2471d31abcfc4cd1c19881 Reviewed-on: https://weave-review.googlesource.com/1342 Reviewed-by: Vitaly Buka <vitalybuka@google.com>