Primary network interface doc tests

[pearcec]

Merge this in with your branch. This should update your PR. Lets see if we can get this into the v0.9.0 release. You might need to cherry-pick into the lastest master. I was working off your branch which is a little stale at this point. Tests works. Only caveat is we need to deploy D3 for the multi-NICs

+ make testacc TEST=./builtin/providers/azurerm TESTARGS=-run=TestAccAzureRMVirtualMachine_primaryNetworkInterfaceId
==> Checking that code complies with gofmt requirements...
go generate $(go list ./... | grep -v /terraform/vendor/)
2017/02/17 10:00:58 Generated command/internal_plugin_list.go
TF_ACC=1 go test ./builtin/providers/azurerm -v -run=TestAccAzureRMVirtualMachine_primaryNetworkInterfaceId -timeout 120
m
=== RUN   TestAccAzureRMVirtualMachine_primaryNetworkInterfaceId
 --- PASS: TestAccAzureRMVirtualMachine_primaryNetworkInterfaceId (560.72s)
PASS
ok      github.com/hashicorp/terraform/builtin/providers/azurerm        560.733s