ARM deploy timeout with expressroute circuit, internal server error

### Issue Details
We where in the process of enabling express route, we hit the following issue, the circuit was deployed but our BGP sessions on our side have not been configured, in this state when we added the following snippet to our complete RG deployment. The case number 117031715470485.

` {
"apiVersion": "2015-06-15",
"type": "Microsoft.Network/connections",
"name": "fra-ams-erc",
"location": "[resourceGroup().location]",
"dependsOn": [
"Microsoft.Network/virtualNetworkGateways/az-erc"
],
"properties": {
"virtualNetworkGateway1": {
"id": "[resourceId('Microsoft.Network/virtualNetworkGateways', parameters('er_NetworkGateway_name'))]"
},
"peer": {
"id": "[resourceId('Microsoft.Network/expressRouteCircuits',parameters('circuitName'))]"
},
"connectionType": "ExpressRoute",
"routingWeight": "20"
}
},
`
This leads to the resouce being created, but the deployment takes forever and finaly fails with internal server error. It seems that this relates to the missing BGP neighbor config on our side, but I would not expect this behaviour of this kind of errror message.

### Repro steps
1.Create VNET with expressroute circuit but BGP sessions down
2.As soon as the connection resource is part of the template it runs into a timeout and internal server error.

Start with the ARM JSON connection snippet and the two listed repro steps, focusing on deployment when the ExpressRoute circuit's BGP sessions are down. Reproduce the timeout and internal server error, then establish whether the behavior is expected and record a concrete template or service-level finding.

Written by the indexing model from the issue text.