Unit tests for Azure scenarios (#495)

* Test firewall rule handling is able to process through the service layer

* Additional tests for authentication and the resource wrapper code

* Positive test case for CreateFirewallRule

* Fixed copyright and usings

src/Microsoft.SqlTools.ResourceProvider.DefaultImpl/AzureResourceManager.cs

@@ -20,7 +20,6 @@ using Microsoft.Rest;
 using System.Globalization;
 using Microsoft.Rest.Azure;
 using Microsoft.SqlTools.ResourceProvider.Core;
-using System.Collections;
 using System.Threading;
 
 namespace Microsoft.SqlTools.ResourceProvider.DefaultImpl