provider/azurerm: fix virtual_machine reading plan as the wrong type (#10626)

TF_ACC=1 go test ./builtin/providers/azurerm -v -run TestAccAzureRMVirtualMachine_plan -timeout 120m
=== RUN   TestAccAzureRMVirtualMachine_plan
--- PASS: TestAccAzureRMVirtualMachine_plan (798.75s)
PASS
ok  	github.com/hashicorp/terraform/builtin/providers/azurerm	798.835s

builtin/providers/azurerm/resource_arm_virtual_machine.go

@@ -582,7 +582,7 @@ func resourceArmVirtualMachineRead(d *schema.ResourceData, meta interface{}) err
 	d.Set("location", resp.Location)
 
 	if resp.Plan != nil {
-		if err := d.Set("plan", flattenAzureRmVirtualMachinePlan(resp.Plan)); err != nil {
+		if err := d.Set("plan", schema.NewSet(resourceArmVirtualMachinePlanHash, flattenAzureRmVirtualMachinePlan(resp.Plan))); err != nil {
 			return fmt.Errorf("[DEBUG] Error setting Virtual Machine Plan error: %#v", err)
 		}
 	}
@@ -788,13 +788,13 @@ func resourceArmVirtualMachineStorageOsProfileWindowsConfigHash(v interface{}) i
 	return hashcode.String(buf.String())
 }
 
-func flattenAzureRmVirtualMachinePlan(plan *compute.Plan) map[string]interface{} {
+func flattenAzureRmVirtualMachinePlan(plan *compute.Plan) []interface{} {
 	result := make(map[string]interface{})
 	result["name"] = *plan.Name
 	result["publisher"] = *plan.Publisher
 	result["product"] = *plan.Product
 
-	return result
+	return []interface{}{result}
 }
 
 func flattenAzureRmVirtualMachineImageReference(image *compute.ImageReference) []interface{} {

builtin/providers/azurerm/resource_arm_virtual_machine_test.go

@@ -392,6 +392,25 @@ func TestAccAzureRMVirtualMachine_changeOSDiskVhdUri(t *testing.T) {
 	})
 }
 
+func TestAccAzureRMVirtualMachine_plan(t *testing.T) {
+	var vm compute.VirtualMachine
+	ri := acctest.RandInt()
+	config := fmt.Sprintf(testAccAzureRMVirtualMachine_plan, ri, ri, ri, ri, ri, ri, ri)
+	resource.Test(t, resource.TestCase{
+		PreCheck:     func() { testAccPreCheck(t) },
+		Providers:    testAccProviders,
+		CheckDestroy: testCheckAzureRMVirtualMachineDestroy,
+		Steps: []resource.TestStep{
+			{
+				Config: config,
+				Check: resource.ComposeTestCheckFunc(
+					testCheckAzureRMVirtualMachineExists("azurerm_virtual_machine.test", &vm),
+				),
+			},
+		},
+	})
+}
+
 func testCheckAzureRMVirtualMachineExists(name string, vm *compute.VirtualMachine) resource.TestCheckFunc {
 	return func(s *terraform.State) error {
 		// Ensure we have enough information in state to look up in API
@@ -2159,3 +2178,98 @@ resource "azurerm_virtual_machine" "test" {
     }
 }
 `
+
+var testAccAzureRMVirtualMachine_plan = `
+resource "azurerm_resource_group" "test" {
+    name = "acctestRG-%d"
+    location = "West US"
+}
+
+resource "azurerm_virtual_network" "test" {
+    name = "acctvn-%d"
+    address_space = ["10.0.0.0/16"]
+    location = "West US"
+    resource_group_name = "${azurerm_resource_group.test.name}"
+}
+
+resource "azurerm_subnet" "test" {
+    name = "acctsub-%d"
+    resource_group_name = "${azurerm_resource_group.test.name}"
+    virtual_network_name = "${azurerm_virtual_network.test.name}"
+    address_prefix = "10.0.2.0/24"
+}
+
+resource "azurerm_network_interface" "test" {
+    name = "acctni-%d"
+    location = "West US"
+    resource_group_name = "${azurerm_resource_group.test.name}"
+
+    ip_configuration {
+    	name = "testconfiguration1"
+    	subnet_id = "${azurerm_subnet.test.id}"
+    	private_ip_address_allocation = "dynamic"
+    }
+}
+
+resource "azurerm_storage_account" "test" {
+    name = "accsa%d"
+    resource_group_name = "${azurerm_resource_group.test.name}"
+    location = "westus"
+    account_type = "Standard_LRS"
+
+    tags {
+        environment = "staging"
+    }
+}
+
+resource "azurerm_storage_container" "test" {
+    name = "vhds"
+    resource_group_name = "${azurerm_resource_group.test.name}"
+    storage_account_name = "${azurerm_storage_account.test.name}"
+    container_access_type = "private"
+}
+
+resource "azurerm_virtual_machine" "test" {
+    name = "acctvm-%d"
+    location = "West US"
+    resource_group_name = "${azurerm_resource_group.test.name}"
+    network_interface_ids = ["${azurerm_network_interface.test.id}"]
+    vm_size = "Standard_DS1_v2"
+
+    storage_image_reference {
+	publisher = "kemptech"
+	offer = "vlm-azure"
+	sku = "freeloadmaster"
+	version = "latest"
+    }
+
+    storage_os_disk {
+        name = "myosdisk1"
+        vhd_uri = "${azurerm_storage_account.test.primary_blob_endpoint}${azurerm_storage_container.test.name}/myosdisk1.vhd"
+        caching = "ReadWrite"
+        create_option = "FromImage"
+        disk_size_gb = "45"
+    }
+
+    os_profile {
+	computer_name = "hostname%d"
+	admin_username = "testadmin"
+	admin_password = "Password1234!"
+    }
+
+    os_profile_linux_config {
+	disable_password_authentication = false
+    }
+
+    plan {
+        name = "freeloadmaster"
+        publisher = "kemptech"
+        product = "vlm-azure"
+    }
+
+    tags {
+    	environment = "Production"
+    	cost-center = "Ops"
+    }
+}
+`