error deploying azure-quickstart-templates/rds-deployment-existing-ad/ complaining about invalid reference

[rds-deployment-existing-ad](azure-quickstart-templates/rds-deployment-existing-ad/)

### Issue Details

After validation of the deployment package. most resource (cb-availabilityset,gw-availabilityset, rdsh-availabilityset, publicIPs, Loadbalancer) get created in the appropriate RG however when it comes to the Microsoft.Network/networkInterfaces they failed with bad request: "error": { "code": "InvalidResourceReference", "message": "Resource; lease make sure that the referenced resource exists, and that both resources are in the same region.

{ "id": "/subscriptions/subscriptionID/resourceGroups/xyz-remoteservices-rg/providers/Microsoft.Resources/deployments/Microsoft.Template/operations/4D68D2E7FFB65874", "operationId": "4D68D2E7FFB65874", "properties": { "provisioningOperation": "Create", "provisioningState": "Failed", "timestamp": "2019-03-06T21:05:23.6606443Z", "duration": "PT3.5947901S", "trackingId": "7ac48f85-3910-4741-b1e4-30c6ebad14b0", "serviceRequestId": "3b3a53a0-e18f-44a4-a5ce-5ab688e77908", "statusCode": "BadRequest", "statusMessage": { "error": { "code": "InvalidResourceReference", "message": "Resource /subscriptions/subscriptionID/resourceGroups/xyz-sharedservices-rg/providers/Microsoft.Network/virtualNetworks/xyz-QA-vnet/subnets/xyz-ActiveDirectory-s referenced by resource /subscriptions/subscriptionID/resourceGroups/xyz-remoteservices-rg/providers/Microsoft.Network/networkInterfaces/rdsh-0-nic was not found. Please make sure that the referenced resource exists, and that both resources are in the same region.", "details": [] } }, "targetResource": { "id": "/subscriptions/subscriptionID/resourceGroups/xyz-remoteservices-rg/providers/Microsoft.Network/networkInterfaces/rdsh-0-nic", "resourceType": "Microsoft.Network/networkInterfaces", "resourceName": "rdsh-0-nic" }, "request": { "content": { "location": "Canada Central", "properties": { "ipConfigurations": [ { "name": "ipconfig", "properties": { "privateIPAllocationMethod": "Dynamic", "subnet": { "id": "/subscriptions/subscriptionID/resourceGroups/xyz-sharedservices-rg/providers/Microsoft.Network/virtualNetworks/xyz-QA-vnet/subnets/xyz-ActiveDirectory-s" } } } ], "dnsSettings": { "dnsServers": [ "10.0.0.4" ] } } } }, "response": { "content": { "error": { "code": "InvalidResourceReference", "message": "Resource /subscriptions/subscriptionID/resourceGroups/xyz-sharedservices-rg/providers/Microsoft.Network/virtualNetworks/xyz-QA-vnet/subnets/xyz-ActiveDirectory-s referenced by resource /subscriptions/subscriptionID/resourceGroups/xyz-remoteservices-rg/providers/Microsoft.Network/networkInterfaces/rdsh-0-nic was not found. Please make sure that the referenced resource exists, and that both resources are in the same region.", "details": [] } } } }}

and so rdsh-0-nic, gw-nic and cb-nic don't get created.

all resources exist in the same RG and in the same region...

### Repro steps (*if necessary, delete otherwise*)
1. deploy the template into Azure sbu
2. fill out information
3. "purchase"
4. validates
5. wait for the deployment to create resources...fails for the nics

Start in azure-quickstart-templates/rds-deployment-existing-ad/ and inspect the network interface definitions and subnet resource IDs used during deployment. Reproduce the listed steps and compare the referenced virtual network and subnet with the NIC deployment locations. Done means rdsh-0-nic, gw-nic, and cb-nic deploy without InvalidResourceReference.

Written by the indexing model from the issue text.