Add test case for VM refresh panic

This adds a test case for @mjrider's new network device polling logic
that fixes several issues resulting from the inconsistencies between
physical devices and IP information when the guest is shut down. The
test is similar to the VM test, but in a second step it powers down the
VM and does another plan. This effectively triggers the panic on the old
code.

vsphere/resource_vsphere_virtual_machine_test.go

@@ -1,14 +1,18 @@
 package vsphere
 
 import (
+	"errors"
 	"fmt"
 	"log"
 	"os"
 	"regexp"
 	"testing"
+	"time"
 
 	"path/filepath"
 
+	"context"
+
 	"github.com/hashicorp/terraform/helper/resource"
 	"github.com/hashicorp/terraform/terraform"
 	"github.com/vmware/govmomi"
@@ -17,7 +21,6 @@ import (
 	"github.com/vmware/govmomi/property"
 	"github.com/vmware/govmomi/vim25/mo"
 	"github.com/vmware/govmomi/vim25/types"
-	"golang.org/x/net/context"
 )
 
 ///////
@@ -294,6 +297,39 @@ func TestAccVSphereVirtualMachine_basic(t *testing.T) {
 	})
 }
 
+func TestAccVSphereVirtualMachine_noPanicShutdown(t *testing.T) {
+	var vm virtualMachine
+	basic_vars := setupTemplateBasicBodyVars()
+	config := basic_vars.testSprintfTemplateBody(testAccCheckVSphereVirtualMachineConfig_really_basic)
+
+	log.Printf("[DEBUG] template= %s", testAccCheckVSphereVirtualMachineConfig_really_basic)
+	log.Printf("[DEBUG] template config= %s", config)
+
+	resource.Test(t, resource.TestCase{
+		PreCheck:     func() { testBasicPreCheck(t) },
+		Providers:    testAccProviders,
+		CheckDestroy: testAccCheckVSphereVirtualMachineDestroy,
+		Steps: []resource.TestStep{
+			resource.TestStep{
+				Config: config,
+				Check: resource.ComposeTestCheckFunc(
+					TestFuncData{vm: vm, label: basic_vars.label}.testCheckFuncBasic(),
+				),
+			},
+			resource.TestStep{
+				PreConfig: func() {
+					if err := testPowerOffVM("terraform-test"); err != nil {
+						panic(err)
+					}
+				},
+				PlanOnly:           true,
+				Config:             config,
+				ExpectNonEmptyPlan: true,
+			},
+		},
+	})
+}
+
 const testAccCheckVSphereVirtualMachineConfig_debug = `
 provider "vsphere" {
   client_debug = true
@@ -1153,6 +1189,45 @@ func TestAccVSphereVirtualMachine_mac_address(t *testing.T) {
 	})
 }
 
+// testPowerOffVM does an immediate power-off of the virtual machine and is
+// used to help set up a refresh scenario where a VM is powered off, which has
+// been a source of panics.
+func testPowerOffVM(name string) error {
+	client := testAccProvider.Meta().(*govmomi.Client)
+	finder := find.NewFinder(client.Client, true)
+
+	dc, err := getDatacenter(client, os.Getenv("VSPHERE_DATACENTER"))
+	if err != nil {
+		return fmt.Errorf("error fetching datacenter: %s", err)
+	}
+
+	finder.SetDatacenter(dc)
+	if err != nil {
+		return fmt.Errorf("error finding datacenter: %s", err)
+	}
+
+	vm, err := finder.VirtualMachine(context.TODO(), name)
+	if err != nil {
+		return err
+	}
+	if vm == nil {
+		return fmt.Errorf("VM not found: %s", name)
+	}
+	task, err := vm.PowerOff(context.TODO())
+	if err != nil {
+		return fmt.Errorf("error powering off VM: %s", err)
+	}
+	ctx, cancel := context.WithTimeout(context.Background(), time.Minute*5)
+	defer cancel()
+	if err := task.Wait(ctx); err != nil {
+		return fmt.Errorf("error waiting for poweroff: %s", err)
+	}
+	if ctx.Err() == context.Canceled {
+		return errors.New("timeout waiting for VM to shutdown")
+	}
+	return nil
+}
+
 func testAccCheckVSphereVirtualMachineDestroy(s *terraform.State) error {
 	client := testAccProvider.Meta().(*govmomi.Client)
 	finder := find.NewFinder(client.Client, true)