New variable kubernetes_cluster_domain

Use cluster_domain/domain variable consistently across all templated files.
All kubeconfig fields contain cluster domain for uniqueness.

Using kubernetes_cluster_domain param now to allow physical servers
to have a different domain from kubernetes cluster if necessary, but
the default keeps them the same.

Change-Id: Ic1e571dc92166b8b603214367f10382fb0ff04b7
diff --git a/README.rst b/README.rst
index 7c2b224..6848d4e 100644
--- a/README.rst
+++ b/README.rst
@@ -102,6 +102,15 @@
         pool:
           verbosity: 2
 
+Set cluster domain
+
+.. code-block:: yaml
+
+    parameters:
+      kubernetes:
+        common:
+          kubernetes_cluster_domain: mycluster.domain
+
 Enable autoscaler for dns addon. Poll period can be skipped.
 
 .. code-block:: yaml