RDS using Existing AD and VNET. - prefixing an "n" to broker.

rds-deployment-existing-ad

### Issue Details
When I run the script after changing the naming convention DSC seems to prepend a "n" to the broker name which causes Powershell to fail trying to add the correct roles as the name of the server is incorrect.

Here is the line to create the name:

"connectionBroker": "[concat('rdstestbroker.',parameters('adDomainName'))]",

In this case the outcome fails connecting to "nrdstestbroker.domainname.com"
The "n" is invalid and I have no idea where it is coming from.

Start with the rds-deployment-existing-ad template and the connectionBroker expression shown in the issue. Reproduce the deployment with the changed naming convention, then trace the DSC or PowerShell step that attempts to connect to the broker. Done means the generated broker name matches the declared name and the required roles are added successfully.

Written by the indexing model from the issue text.