provider/azurerm: Add `azurerm_virtual_machine` Acceptance Test for (#7456)
provider/azurerm: Add `azurerm_virtual_machine` Acceptance Test for (#7456)

`storage_data_disk`

```
make testacc TEST=./builtin/providers/azurerm TESTARGS='-run=TestAccAzureRMVirtualMachine_withDataDisk'
==> Checking that code complies with gofmt requirements...
/Users/stacko/Code/go/bin/stringer
go generate $(go list ./... | grep -v /vendor/)
2016/07/01 15:47:13 Generated command/internal_plugin_list.go
TF_ACC=1 go test ./builtin/providers/azurerm -v
-run=TestAccAzureRMVirtualMachine_withDataDisk -timeout 120m
=== RUN   TestAccAzureRMVirtualMachine_withDataDisk
--- PASS: TestAccAzureRMVirtualMachine_withDataDisk (575.39s)
PASS
ok      github.com/hashicorp/terraform/builtin/providers/azurerm
```
sebastus/terraform-provider-azurerm,sebastus/terraform-provider-azurerm,thiagocaiubi/terraform-provider-azurerm,thiagocaiubi/terraform-provider-azurerm,sebastus/terraform-provider-azurerm,abhijeetgaiha/terraform-provider-azurerm,abhijeetgaiha/terraform-provider-azurerm,abhijeetgaiha/terraform-provider-azurerm,thiagocaiubi/terraform-provider-azurerm