Fix failing acceptance tests by using case insensitive diff function.

Some resource fail due to resource_group_name always being stored as
lowercase. For those resources we add the case insensitive diff
function.

builtin/providers/azurerm/resource_arm_dns_zone.go

@@ -29,6 +29,7 @@ func resourceArmDnsZone() *schema.Resource {
 				Type:             schema.TypeString,
 				Required:         true,
 				ForceNew:         true,
+				DiffSuppressFunc: resourceAzurermResourceGroupNameDiffSuppress,
 			},
 
 			"number_of_record_sets": &schema.Schema{

builtin/providers/azurerm/resource_arm_traffic_manager_endpoint.go

@@ -89,6 +89,7 @@ func resourceArmTrafficManagerEndpoint() *schema.Resource {
 				Type:             schema.TypeString,
 				Required:         true,
 				ForceNew:         true,
+				DiffSuppressFunc: resourceAzurermResourceGroupNameDiffSuppress,
 			},
 		},
 	}

builtin/providers/azurerm/resource_arm_traffic_manager_profile.go

@@ -96,6 +96,7 @@ func resourceArmTrafficManagerProfile() *schema.Resource {
 				Type:             schema.TypeString,
 				Required:         true,
 				ForceNew:         true,
+				DiffSuppressFunc: resourceAzurermResourceGroupNameDiffSuppress,
 			},
 
 			"tags": tagsSchema(),