Move the ResourceGroup filtering for GetCertificates to the server

Author: Nicholas King

src/Websites/Websites/Utilities/CmdletHelpers.cs

@@ -394,14 +394,10 @@ internal static Certificate[] GetCertificates(ResourceClient resourceClient, Web
         {
             var certificateResources = resourceClient.ResourceManagementClient.FilterResources(new FilterResourcesOptions
             {
+                ResourceGroup = resourceGroupName,
                 ResourceType = "Microsoft.Web/Certificates"
             }).ToArray();
 
-            if (!string.IsNullOrEmpty(resourceGroupName))
-            {
-                certificateResources = certificateResources.Where(c => string.Equals(c.ResourceGroupName, resourceGroupName, StringComparison.OrdinalIgnoreCase)).ToArray();
-            }
-
             var certificates =
                 certificateResources.Select(
                     certificateResource =>