Fix parallel acctest race on Provider

We should not initialize providers for every test, in which case it
might cause the global provider not same as the actual used provider in
each test. And might results into panic when user trying to retrive meta
from global provider when testing resource exist/destroy.

azurerm/internal/acceptance/data.go

@@ -5,6 +5,7 @@ import (
 	"math"
 	"os"
 	"strconv"
+	"sync"
 	"testing"
 
 	"github.com/Azure/go-autorest/autorest/azure"
@@ -17,6 +18,8 @@ import (
 	"github.com/terraform-providers/terraform-provider-azurerm/azurerm/internal/provider"
 )
 
+var once sync.Once
+
 type TestData struct {
 	// Locations is a set of Azure Regions which should be used for this Test
 	Locations Regions
@@ -48,13 +51,15 @@ type TestData struct {
 
 // BuildTestData generates some test data for the given resource
 func BuildTestData(t *testing.T, resourceType string, resourceLabel string) TestData {
-	azureProvider := provider.AzureProvider().(*schema.Provider)
+	once.Do(func() {
+		azureProvider := provider.AzureProvider().(*schema.Provider)
 
-	AzureProvider = azureProvider
-	SupportedProviders = map[string]terraform.ResourceProvider{
-		"azurerm": azureProvider,
-		"azuread": azuread.Provider().(*schema.Provider),
-	}
+		AzureProvider = azureProvider
+		SupportedProviders = map[string]terraform.ResourceProvider{
+			"azurerm": azureProvider,
+			"azuread": azuread.Provider().(*schema.Provider),
+		}
+	})
 
 	env, err := Environment()
 	if err != nil {