add cert_source param

Change-Id: Icfb18ecb679a6c665ae90dee814962dfc86ef695
diff --git a/kubernetes/master/controller.sls b/kubernetes/master/controller.sls
index cb4746f..d8c453c 100644
--- a/kubernetes/master/controller.sls
+++ b/kubernetes/master/controller.sls
@@ -120,7 +120,7 @@
 
 /etc/kubernetes/ssl/{{ filename }}:
   file.managed:
-    - source: salt://_certs/kubernetes/{{ filename }}
+    - source: salt://{{ master.get('cert_source','_certs/kubernetes') }}/{{ filename }}
     - user: root
     - group: haproxy
     - mode: 640