Making the alias a variable to be replaced by the code.

cluster/juju/charms/trusty/kubernetes-master/files/distribution.conf.tmpl

@@ -1,6 +1,6 @@
 server {
     listen %(api_bind_address)s:80;
     location %(web_uri)s {
-        alias /opt/kubernetes/_output/local/bin/linux/amd64/;
+        alias %(alias)s;
     }
 }