examples: Fix examples to work with Terraform v0.11.x

* Explicitly pass provider modules to satisfy constraints
* https://github.com/hashicorp/terraform/issues/16824

examples/terraform/bootkube-install/README.md

@@ -9,7 +9,7 @@ Follow the getting started [tutorial](../../../Documentation/getting-started.md)
 * Matchbox v0.6+ [installation](../../../Documentation/deployment.md) with gRPC API enabled
 * Matchbox provider credentials `client.crt`, `client.key`, and `ca.crt`
 * PXE [network boot](../../../Documentation/network-setup.md) environment
-* Terraform v0.9+ and [terraform-provider-matchbox](https://github.com/coreos/terraform-provider-matchbox) installed locally on your system
+* Terraform v0.10.x or v0.11.x and [terraform-provider-matchbox](https://github.com/coreos/terraform-provider-matchbox) installed locally on your system
 * Machines with known DNS names and MAC addresses
 
 If you prefer to provision QEMU/KVM VMs on your local Linux machine, set up the matchbox [development environment](../../../Documentation/getting-started-rkt.md).

examples/terraform/bootkube-install/cluster.tf

@@ -2,6 +2,13 @@
 module "cluster" {
   source = "git::https://github.com/poseidon/typhoon//bare-metal/container-linux/kubernetes?ref=v1.8.4"
 
+  providers = {
+    local = "local.default"
+    null = "null.default"
+    template = "template.default"
+    tls = "tls.default"
+  }
+
   # install
   matchbox_http_endpoint  = "${var.matchbox_http_endpoint}"
   container_linux_channel = "${var.container_linux_channel}"

examples/terraform/bootkube-install/provider.tf

@@ -5,3 +5,23 @@ provider "matchbox" {
   client_key  = "${file("~/.matchbox/client.key")}"
   ca          = "${file("~/.matchbox/ca.crt")}"
 }
+
+provider "local" {
+  version = "~> 1.0"
+  alias = "default"
+}
+
+provider "null" {
+  version = "~> 1.0"
+  alias = "default"
+}
+
+provider "template" {
+  version = "~> 1.0"
+  alias = "default"
+}
+
+provider "tls" {
+  version = "~> 1.0"
+  alias = "default"
+}