Remove client side validation for azure network plugin (#1798)

* 🐛 (Network profile of AKS.) Remove client side validation for azure network plugin.

Non-empty podCidr string validation for azure network plugin should be handled by ASK service.

* 📝 (Network profile of AKS.) Add more explainations for network_profile.

Add more explainations on default network_profile and `azure` specific validation requirement.

* Updating to better match the other docs

azurerm/resource_arm_kubernetes_cluster.go

@@ -39,12 +39,6 @@ func resourceArmKubernetesCluster() *schema.Resource {
 					return nil
 				}
 
-				podCidr := profile["pod_cidr"].(string)
-
-				if networkPlugin == "azure" && podCidr != "" {
-					return fmt.Errorf("The `pod_cidr` field in the `network_profile` block can not be specified when `network_plugin` is set to `azure`. Please remove `pod_cidr` or set `network_plugin` to `kubenet`.")
-				}
-
 				dockerBridgeCidr := profile["docker_bridge_cidr"].(string)
 				dnsServiceIP := profile["dns_service_ip"].(string)
 				serviceCidr := profile["service_cidr"].(string)

website/docs/r/kubernetes_cluster.html.markdown

@@ -193,6 +193,7 @@ The following arguments are supported:
 * `kubernetes_version` - (Optional) Version of Kubernetes specified when creating the AKS managed cluster. If not specified, the latest recommended version will be used at provisioning time (but won't auto-upgrade).
 
 * `network_profile` - (Optional) A Network Profile block as documented below.
+-> **NOTE:** If `network_profile` is not defined, `kubenet` profile will be used by default.
 
 * `tags` - (Optional) A mapping of tags to assign to the resource.
 
@@ -265,7 +266,7 @@ A `network_profile` block supports the following:
 
 * `docker_bridge_cidr` - (Optional) IP address (in CIDR notation) used as the Docker bridge IP address on nodes. This is required when `network_plugin` is set to `kubenet`. Changing this forces a new resource to be created.
 
-* `pod_cidr` - (Optional) The CIDR to use for pod IP addresses. Changing this forces a new resource to be created.
+* `pod_cidr` - (Optional) The CIDR to use for pod IP addresses. This field can only be set when `network_plugin` is set to `kubenet`. Changing this forces a new resource to be created.
 
 Here's an example of configuring the `kubenet` Networking Profile: