Allow more complex docker login

Change-Id: I02343fa031a0ea271d74a23ade0b1149ebc2424e
diff --git a/docker/host.sls b/docker/host.sls
index 3a6d1d4..60b3cca 100644
--- a/docker/host.sls
+++ b/docker/host.sls
@@ -81,10 +81,11 @@
 
 {%- for name,registry in host.registry.iteritems() %}
 
-docker_{{ registry.address }}_login:
+docker_{{ registry.get('address', name) }}_login:
   cmd.run:
-  - name: 'docker login -u {{ registry.user }} -p {{ registry.password }} {{ registry.address }}'
-  - unless: grep {{ registry.address }} /root/.docker/config.json
+  - name: 'docker login -u {{ registry.user }} -p {{ registry.password }}{% if registry.get('address') %} {{ registry.address }}{% endif %}'
+  - user: {{ registry.get('system_user', 'root') }}
+  - unless: grep {{ registry.address|default('https://index.docker.io/v1/') }} {{ salt['user.info'](registry.get('system_user', 'root')).home }}/.docker/config.json
 
 {%- endfor %}