Prevent crash when client.enabled isn't defined

Change-Id: I29a526767d4f608edf50c4c599799ca2df7603f9
diff --git a/docker/client/init.sls b/docker/client/init.sls
index 2286f9d..e99aa8b 100644
--- a/docker/client/init.sls
+++ b/docker/client/init.sls
@@ -1,5 +1,5 @@
 {% from "docker/map.jinja" import client with context %}
-{%- if client.enabled %}
+{%- if client.get('enabled') %}
 
 include:
   {%- if client.network is defined %}