Currently, when the endpoint is unavailable, Free Monitoring will continue to retry in the backound. The retries are useful when free monitoring is enabled via the command-line or when mongod is restarted with free monitoring already enabled. When it is initiated via the shell, it is confusing to return "null" to the user, and we may want to consider aborting the registration instead of retrying.

> db.enableFreeMonitoring()
Successfully initiated free monitoring. The registration is proceeding in the background. 
Run db.getFreeMonitoringStatus() at any time to check on the progress.
null