How to use cloud-init rh_subscription plugin to register an instance on boot in Red Hat OpenStack Platform

Issue

Red Hat Enterprise Linux 7.2 and above provide the rh_subscription plugin which is run on boot of the RHEL cloud image as part of cloud-init
since Bugzilla 1227393

[   30.312499] cloud-init[797]: 2016-09-08 12:17:18,339 - cc_rh_subscription.py[WARNING]: Unable to register system due to incomplete information.
[   30.339313] cloud-init[797]: 2016-09-08 12:17:18,343 - cc_rh_subscription.py[WARNING]: Use either activationkey and org *or* userid and password
[   30.376519] cloud-init[797]: 2016-09-08 12:17:18,343 - cc_rh_subscription.py[WARNING]: Registration failed or did not run completely
[   30.400571] cloud-init[797]: 2016-09-08 12:17:18,343 - cc_rh_subscription.py[WARNING]: rh_subscription plugin did not complete successfully

1. How can this be used to register an instance on first boot?
2. Is it possible to disable rh_subscription plugin to remove the WARNING messages?