Add support for Packet with Terraform (#4043)

* Add support for Packet with Terraform

Co-Author: johnstudarus <john@jhlconsulting.com>

* removed advanced features to streamline

* clarifying usage

* Update README.md

provide a better test to validate things are working OK

* Update README.md

clarifying what to set

* minor wordsmithing

* Fix admin cert path

* clarifying how to configure keys

* enabling kubeconfig_localhost

pull over the configuration file via playbooks rather than the key files individually

* Create output.tf

* Add support for node specific plans

contrib/terraform/packet/output.tf

@@ -0,0 +1,15 @@
+output "k8s_masters" {
+    value = "${packet_device.k8s_master.*.access_public_ipv4}"
+}
+
+output "k8s_masters_no_etc" {
+    value = "${packet_device.k8s_master_no_etcd.*.access_public_ipv4}"
+}
+
+output "k8s_etcds" {
+    value = "${packet_device.k8s_etcd.*.access_public_ipv4}"
+}
+
+output "k8s_nodes" {
+    value = "${packet_device.k8s_node.*.access_public_ipv4}"
+}