Fix autoscale example to use singular AD datasource

Author: alexng-canuck

docs/examples/autoscaling/compute.tf

@@ -1,7 +1,7 @@
 // Copyright (c) 2017, 2019, Oracle and/or its affiliates. All rights reserved.
 
 resource "oci_core_instance" "TFInstance" {
-  availability_domain = "${lookup(data.oci_identity_availability_domains.ADs.availability_domains[var.availability_domain - 1],"name")}"
+  availability_domain = "${data.oci_identity_availability_domain.AD.name}"
   compartment_id      = "${var.compartment_ocid}"
   display_name        = "TFInstanceForInstancePool"
   shape               = "${var.instance_shape}"
@@ -63,7 +63,7 @@ resource "oci_core_instance_pool" "TFInstancePool" {
   display_name              = "TFInstancePool"
 
   placement_configurations {
-    availability_domain = "${lookup(data.oci_identity_availability_domains.ADs.availability_domains[var.availability_domain - 1],"name")}"
+    availability_domain = "${data.oci_identity_availability_domain.AD.name}"
     primary_subnet_id   = "${oci_core_subnet.ExampleSubnet.id}"
   }
 }

docs/examples/autoscaling/datasources.tf

@@ -1,8 +1,9 @@
 // Copyright (c) 2017, 2019, Oracle and/or its affiliates. All rights reserved.
 
 # Gets a list of Availability Domains
-data "oci_identity_availability_domains" "ADs" {
+data "oci_identity_availability_domain" "AD" {
   compartment_id = "${var.tenancy_ocid}"
+  ad_number      = "1"
 }
 
 data "oci_core_instance_configuration" TFInstanceConfigurationDatasource {

docs/examples/autoscaling/network.tf

@@ -8,7 +8,7 @@ resource "oci_core_virtual_network" "ExampleVCN" {
 }
 
 resource "oci_core_subnet" "ExampleSubnet" {
-  availability_domain = "${lookup(data.oci_identity_availability_domains.ADs.availability_domains[var.availability_domain - 1],"name")}"
+  availability_domain = "${data.oci_identity_availability_domain.AD.name}"
   cidr_block          = "10.1.20.0/24"
   display_name        = "TFExampleSubnet"
   dns_label           = "tfexamplesubnet"